TY - BOOK
TI - World Scientific handbook of organic optoelectronic devices
A3 - So, Franky
A3 - Huang, Jinsong
A3 - Yongbo, Yuan
A3 - Thompson, Barry C.
DA - 2018///
PY - 2018///
PB - World Scientific Publishing Company
ER -
TY - JOUR
TI - Soft X-ray Microscopy: History, Status, and Future
AU - Ade, Harald
T2 - Microscopy and Microanalysis
AB - An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
DA - 2018/8//
PY - 2018/8//
DO - 10.1017/S1431927618005494
VL - 24
IS - S1
SP - 1000-1001
J2 - Microsc Microanal
LA - en
OP -
SN - 1431-9276 1435-8115
UR - http://dx.doi.org/10.1017/S1431927618005494
DB - Crossref
ER -
TY - JOUR
TI - Long-Lived, Non-Geminate, Radiative Recombination of Photogenerated Charges in a Polymer/Small-Molecule Acceptor Photovoltaic Blend
AU - Ziffer, Mark E.
AU - Jo, Sae Byeok
AU - Zhong, Hongliang
AU - Ye, Long
AU - Liu, Hongbin
AU - Lin, Francis
AU - Zhang, Jie
AU - Li, Xiaosong
AU - Ade, Harald W.
AU - Jen, Alex K.-Y.
AU - Ginger, David S.
T2 - Journal of the American Chemical Society
AB - Minimization of open-circuit-voltage ( VOC) loss is required to transcend the efficiency limitations on the performance of organic photovoltaics (OPV). We study charge recombination in an OPV blend comprising a polymer donor with a small molecule nonfullerene acceptor that exhibits both high photovoltaic internal quantum efficiency and relatively high external electroluminescence quantum efficiency. Notably, this donor/acceptor blend, consisting of the donor polymer commonly referred to as PCE10 with a pseudoplanar small molecule acceptor (referred to as FIDTT-2PDI) exhibits relatively bright delayed photoluminescence on the microsecond time scale beyond that observed in the neat material. We study the photoluminescence decay kinetics of the blend in detail and conclude that this long-lived photoluminescence arises from radiative nongeminate recombination of charge carriers, which we propose occurs via a donor/acceptor CT state located close in energy to the singlet state of the polymer donor. Additionally, crystallographic and spectroscopic studies point toward low subgap disorder, which could be beneficial for low radiative and nonradiative losses. These results provide an important demonstration of photoluminescence due to nongeminate charge recombination in an efficient OPV blend, a key step in identifying new OPV materials and materials-screening criteria if OPV is to approach the theoretical limits to efficiency.
DA - 2018/7/14/
PY - 2018/7/14/
DO - 10.1021/JACS.8B05834
VL - 140
IS - 31
SP - 9996-10008
J2 - J. Am. Chem. Soc.
LA - en
OP -
SN - 0002-7863 1520-5126
UR - http://dx.doi.org/10.1021/JACS.8B05834
DB - Crossref
ER -
TY - JOUR
TI - Controlling Blend Morphology for Ultrahigh Current Density in Nonfullerene Acceptor-Based Organic Solar Cells
AU - Song, Xin
AU - Gasparini, Nicola
AU - Ye, Long
AU - Yao, Huifeng
AU - Hou, Jianhui
AU - Ade, Harald
AU - Baran, Derya
T2 - ACS Energy Letters
AB - In this Letter, we highlight a system with a well-known polymer donor (PTB7-Th) blended with a narrow band gap nonfullerene acceptor (IEICO-4F) as the active layer and 1-chloronaphthalene (CN) as the solvent additive. Optimization of the photoactive layer nanomorphology yields a short-circuit current density value of 27.3 mA/cm2, one of the highest values in organic solar cells reported to date, which competes with other types of solution-processed solar cells such as perovskite or quantum dot devices. Along with decent open-circuit voltage (0.71 V) and fill factor values (66%), a power conversion efficiency of 12.8% is achieved for the champion devices. Morphology characterizations elucidate that the origin of this high photocurrent is mainly the increased π–π coherence length of the acceptor, the domain spacing, as well as the mean-square composition variation of the blend. Optoelectronic measurements confirm a balanced hole and electron mobility and reduced trap-assisted recombination for the best devices.
DA - 2018/1/23/
PY - 2018/1/23/
DO - 10.1021/ACSENERGYLETT.7B01266
VL - 3
IS - 3
SP - 669-676
J2 - ACS Energy Lett.
LA - en
OP -
SN - 2380-8195 2380-8195
UR - http://dx.doi.org/10.1021/ACSENERGYLETT.7B01266
DB - Crossref
ER -
TY - JOUR
TI - Polymer Solar Cells: Miscibility-Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation (Adv. Energy Mater. 28/2018)
AU - Ye, Long
AU - Collins, Brian A.
AU - Jiao, Xuechen
AU - Zhao, Jingbo
AU - Yan, He
AU - Ade, Harald
T2 - Advanced Energy Materials
AB - In article number 1703058, Harald Ade and co-workers present the determination of liquidus miscibility and its temperature dependence of organic films by scanning transmission X-ray microscopy and outline an approach to convert liquidus miscibility to an effective Flory-Huggins interaction parameter χ, which will pave a way to predict morphology and processing strategies of polymer solar cells.
DA - 2018/10//
PY - 2018/10//
DO - 10.1002/AENM.201870124
VL - 8
IS - 28
SP - 1870124
J2 - Adv. Energy Mater.
LA - en
OP -
SN - 1614-6832
UR - http://dx.doi.org/10.1002/AENM.201870124
DB - Crossref
ER -
TY - JOUR
TI - Surpassing 10% Efficiency Benchmark for Nonfullerene Organic Solar Cells by Scalable Coating in Air from Single Nonhalogenated Solvent
AU - Ye, Long
AU - Xiong, Yuan
AU - Zhang, Qianqian
AU - Li, Sunsun
AU - Wang, Cheng
AU - Jiang, Zhang
AU - Hou, Jianhui
AU - You, Wei
AU - Ade, Harald
T2 - Advanced Materials
AB - The commercialization of nonfullerene organic solar cells (OSCs) critically relies on the response under typical operating conditions (for instance, temperature and humidity) and the ability of scale-up. Despite the rapid increase in power conversion efficiency (PCE) of spin-coated devices fabricated in a protective atmosphere, the efficiencies of printed nonfullerene OSC devices by blade coating are still lower than 6%. This slow progress significantly limits the practical printing of high-performance nonfullerene OSCs. Here, a new and relatively stable nonfullerene combination is introduced by pairing the nonfluorinated acceptor IT-M with the polymeric donor FTAZ. Over 12% efficiency can be achieved in spin-coated FTAZ:IT-M devices using a single halogen-free solvent. More importantly, chlorine-free, blade coating of FTAZ:IT-M in air is able to yield a PCE of nearly 11% despite a humidity of ≈50%. X-ray scattering results reveal that large π-π coherence length, high degree of face-on orientation with respect to the substrate, and small domain spacing of ≈20 nm are closely correlated with such high device performance. The material system and approach yield the highest reported performance for nonfullerene OSC devices by a coating technique approximating scalable fabrication methods and hold great promise for the development of low-cost, low-toxicity, and high-efficiency OSCs by high-throughput production.
DA - 2018/1/10/
PY - 2018/1/10/
DO - 10.1002/ADMA.201705485
VL - 30
IS - 8
SP - 1705485
J2 - Adv. Mater.
LA - en
OP -
SN - 0935-9648
UR - http://dx.doi.org/10.1002/ADMA.201705485
DB - Crossref
KW - blade coating
KW - film morphology
KW - nonfullerene acceptors
KW - nonhalogenated solvents
KW - organic solar cells
ER -
TY - JOUR
TI - Enhanced piezoelectricity of thin film hafnia-zirconia (HZO) by inorganic flexible substrates
AU - Hsain, H. Alex
AU - Sharma, Pankaj
AU - Yu, Hyeonggeun
AU - Jones, Jacob L.
AU - So, Franky
AU - Seidel, Jan
T2 - Applied Physics Letters
AB - Hf0.5Zr0.5O2 (HZO) films are grown on rigid glass and flexible polyimide substrates using non-rapid thermal annealing. Films are comparatively investigated using macroscopic and local probe-based approaches to characterize their ferroelectric and piezoelectric properties. The polarization-electric field (P-E) measurements reveal that the ferroelectric characteristics of these thin films agree with the observed switchable piezoresponse hysteresis loops as well as electrically written, oppositely oriented domains. Moreover, the HZO thin films grown on flexible polyimide substrates display significantly enhanced piezoelectric response in comparison to the films grown on rigid substrates. This effect is likely due to improved domain wall motion caused by the mechanical release of the film-substrate couple. These findings suggest that inherently lead-free HZO thin films on flexible substrates are potential candidate materials for improved piezoelectric applications in wearable devices.
DA - 2018/7/9/
PY - 2018/7/9/
DO - 10.1063/1.5031134
VL - 113
IS - 2
SP - 022905
J2 - Appl. Phys. Lett.
LA - en
OP -
SN - 0003-6951 1077-3118
UR - http://dx.doi.org/10.1063/1.5031134
DB - Crossref
ER -
TY - JOUR
TI - Semi-transparent vertical organic light-emitting transistors
AU - Yu, Hyeonggeun
AU - Ho, Szuheng
AU - Barange, Nilesh
AU - Larrabee, Ryan
AU - So, Franky
T2 - Organic Electronics
AB - Vertical organic light-emitting transistor (VOLET) having an organic light-emitting diode integrated with a vertical thin-film transistor is promising for transparent electronics because the vertical device structure potentially offers a display with a large aperture ratio and a low power consumption. However, making a transparent VOLET has been challenging due to the requirements for all transparent electrodes including fabrication of a porous source electrode for current modulation in the device. Here, we report a semi-transparent VOLET with a large modulation of light emitted through the top and bottom electrodes using a nano-porous indium-tin oxide (ITO) source electrode, a Mg:Ag drain electrode, and an ITO gate electrode. The porous ITO source electrode is not only important for luminance modulation, but the nano-textured film morphology also enhances light extraction from the device. Finally, we show that the off current of the VOLET can be suppressed with an electron transporting layer (C60), leading to a large luminance on/off ratio of 104.
DA - 2018/4//
PY - 2018/4//
DO - 10.1016/J.ORGEL.2018.01.030
VL - 55
SP - 126-132
J2 - Organic Electronics
LA - en
OP -
SN - 1566-1199
UR - http://dx.doi.org/10.1016/J.ORGEL.2018.01.030
DB - Crossref
KW - Vertical field effect transistor
KW - Light-emitting transistor
KW - Light extraction
KW - Transparent electronic
KW - Porous electrode
ER -
TY - JOUR
TI - Vertical Organic-Inorganic Hybrid Perovskite Schottky Junction Transistors
AU - Yu, Hyeonggeun
AU - Cheng, Yuanhang
AU - Shin, Donghun
AU - Tsang, Sai-Wing
AU - So, Franky
T2 - Advanced Electronic Materials
AB - Abstract While organolead halide perovskite materials have attracted considerable attention for high efficiency solar cells, they have shown little potential for use in field‐effect transistors (FETs) due to the limited current modulation at room temperature. Here, by developing a vertically gated methylammonium lead iodide (MAPbI 3 )/indium‐tin oxide (ITO) Schottky junction, a room temperature‐operable vertical MAPbI 3 thin‐film transistor is reported. Due to the injection‐controlled gating mechanism as well as the vertical channel structure, a current modulation ratio up to 10 4 is achieved. Fabrication of a nanoporous ITO source electrode forming a highly rectifying Schottky junction with the MAPbI 3 layer is the key for the large current modulation. It is discovered that the electron transporting layers on top of the MAPbI 3 layer play an important role in achieving a large current rectification of 10 7 at the Schottky junction and hence large current on/off ratios of the resulting transistor.
DA - 2018/3/22/
PY - 2018/3/22/
DO - 10.1002/AELM.201800039
VL - 4
IS - 5
SP - 1800039
J2 - Adv. Electron. Mater.
LA - en
OP -
SN - 2199-160X
UR - http://dx.doi.org/10.1002/AELM.201800039
DB - Crossref
KW - organic-inorganic hybrid perovskite
KW - patterned electrodes
KW - Schottky junctions
KW - vertical transistors
ER -
TY - JOUR
TI - Impact of Nonfullerene Molecular Architecture on Charge Generation, Transport, and Morphology in PTB7-Th-Based Organic Solar Cells
AU - Yi, Xueping
AU - Gautam, Bhoj
AU - Constantinou, Iordania
AU - Cheng, Yuanhang
AU - Peng, Zhengxing
AU - Klump, Erik
AU - Ba, Xiaochu
AU - Ho, Carr Hoi Yi
AU - Dong, Chen
AU - Marder, Seth R.
AU - Reynolds, John R.
AU - Tsang, Sai-Wing
AU - Ade, Harald
AU - So, Franky
T2 - Advanced Functional Materials
AB - Abstract Despite the rapid development of nonfullerene acceptors (NFAs), the fundamental understanding on the relationship between NFA molecular architecture, morphology, and device performance is still lacking. Herein, poly[[4,8‐bis[5‐(2‐ethylhexyl)thiophene‐2‐yl]benzo[1,2‐b:4,5‐b0]dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]‐thieno[3,4‐b]thiophenediyl]] (PTB7‐Th) is used as the donor polymer to compare an NFA with a 3D architecture (SF‐PDI4) to a well‐studied NFA with a linear acceptor–donor–acceptor (A–D–A) architecture (ITIC). The data suggest that the NFA ITIC with a linear molecular structure shows a better device performance due to an increase in short‐circuit current ( J sc ) and fill factor (FF) compared to the 3D SF‐PDI4. The charge generation dynamics measured by femtosecond transient absorption spectroscopy (TAS) reveals that the exciton dissociation process in the PTB7‐Th:ITIC films is highly efficient. In addition, the PTB7‐Th:ITIC blend shows a higher electron mobility and lower energetic disorder compared to the PTB7‐Th:SF‐PDI4 blend, leading to higher values of J sc and FF. The compositional sensitive resonant soft X‐ray scattering (R‐SoXS) results indicate that ITIC molecules form more pure domains with reduced domain spacing, resulting in more efficient charge transport compared with the SF‐PDI4 blend. It is proposed that both the molecular structure and the corresponding morphology of ITIC play a vital role for the good solar cell device performance.
DA - 2018/6/21/
PY - 2018/6/21/
DO - 10.1002/ADFM.201802702
VL - 28
IS - 32
SP - 1802702
J2 - Adv. Funct. Mater.
LA - en
OP -
SN - 1616-301X
UR - http://dx.doi.org/10.1002/ADFM.201802702
DB - Crossref
KW - charge generation
KW - charge transport
KW - molecular architecture
KW - morphology
KW - nonfullerene acceptors
ER -
TY - JOUR
TI - Increased Exciton Delocalization of Polymer upon Blending with Fullerene
AU - Gautam, Bhoj
AU - Klump, Erik
AU - Yi, Xueping
AU - Constantinou, Iordania
AU - Shewmon, Nathan
AU - Salehi, Amin
AU - Lo, Chi Kin
AU - Zheng, Zilong
AU - Brédas, Jean-Luc
AU - Gundogdu, Kenan
AU - Reynolds, John R.
AU - So, Franky
T2 - Advanced Materials
AB - Abstract Interfaces between donor and acceptor in a polymer solar cell play a crucial role in exciton dissociation and charge photogeneration. While the importance of charge transfer (CT) excitons for free carrier generation is intensively studied, the effect of blending on the nature of the polymer excitons in relation to the blend nanomorphology remains largely unexplored. In this work, electroabsorption (EA) spectroscopy is used to study the excited‐state polarizability of polymer excitons in several polymer:fullerene blend systems, and it is found that excited‐state polarizability of polymer excitons in the blends is a strong function of blend nanomorphology. The increase in excited‐state polarizability with decreased domain size indicates that intermixing of states at the interface between the donor polymers and fullerene increases the exciton delocalization, resulting in an increase in exciton dissociation efficiency. This conclusion is further supported by transient absorption spectroscopy and time‐resolved photoluminescence measurements, along with the results from time‐dependent density functional theory calculations. These findings indicate that polymer excited‐state polarizability is a key parameter for efficient free carrier generation and should be considered in the design and development of high‐performance polymer solar cells.
DA - 2018/6/11/
PY - 2018/6/11/
DO - 10.1002/adma.201801392
VL - 30
IS - 30
SP - 1801392
J2 - Adv. Mater.
LA - en
OP -
SN - 0935-9648
UR - http://dx.doi.org/10.1002/adma.201801392
DB - Crossref
KW - charge transfer states
KW - electroabsorption
KW - exciton delocalization
KW - Frenkel exciton
KW - polarizability
ER -
TY - JOUR
TI - Randomly Distributed Conjugated Polymer Repeat Units for High-Efficiency Photovoltaic Materials with Enhanced Solubility and Processability
AU - Xu, Bing
AU - Pelse, Ian
AU - Agarkar, Shruti
AU - Ito, Shunichiro
AU - Zhang, Junxiang
AU - Yi, Xueping
AU - Chujo, Yoshiki
AU - Marder, Seth
AU - So, Franky
AU - Reynolds, John R.
AU - al.
T2 - ACS APPLIED MATERIALS & INTERFACES
AB - Three structurally disordered terpolymer derivatives of PffBT4T-2OD (PCE11), prepared by replacing a varied amount of bithiophene linkers with single thiophenes, were found to exhibit reduced aggregation in solution with increasing thiophene content, while important redox and optoelectronic properties remained similar to those of PffBT4T-2OD. Solar cells based on random terpolymer-PC71BM blends exhibited average power conversion efficiencies of over 9.5% when processed with preheated substrates, with fill factors above 70%, exceeding those from PffBT4T-2OD. Thanks to increased solubility, random terpolymer devices were able to be fabricated on room-temperature substrates, reaching virtually identical performance among all three polymers despite remarkable thicknesses of ∼400 nm. Thus, we show that the random terpolymer approach is successful in improving processability while maintaining device performance.
DA - 2018/12/26/
PY - 2018/12/26/
DO - 10.1021/acsami.8b15522
VL - 10
IS - 51
SP - 44583-44588
SN - 1944-8244
KW - conjugated polymers
KW - organic photovoltaics
KW - random terpolymers
KW - bulk heterojunction solar cells
KW - organic electronics
ER -
TY - JOUR
TI - Donor polymer based on alkylthiophene side chains for efficient non- fullerene organic solar cells: insights into fluorination and side chain effects on polymer aggregation and blend morphology
AU - Liu, Jing
AU - Ma, Lik-Kuen
AU - Li, Zhengke
AU - Hu, Huawei
AU - Sheong, Fu Kit
AU - Zhang, Guangye
AU - Ade, Harald
AU - Yan, He
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - The synergistic effects of overfluorination and alkylthiophene side chain strategies led to 10.60% efficiency for non-fullerene organic solar cells.
DA - 2018/12/14/
PY - 2018/12/14/
DO - 10.1039/c8ta08769e
VL - 6
IS - 46
SP - 23270-23277
SN - 2050-7496
ER -
TY - JOUR
TI - Side-Chain Sequence Enabled Regioisomeric Acceptors for Conjugated Polymers
AU - Luo, Xuyi
AU - Tran, Dung T.
AU - Kadlubowski, Natalie M.
AU - Ho, Carr Hoi Yi
AU - Riley, Parand
AU - So, Franky
AU - Mei, Jianguo
T2 - MACROMOLECULES
AB - Side-chain sequence enabled regioisomeric acceptors, bearing different side-chain sequences on the same conjugated backbone, are herein reported. Two regioregular polymers PTBI-1 and PTBI-2 and one regiorandom polymer PTBI-3 were synthesized from these two regioisomeric acceptors for a comparative study. UV–vis–NIR absorption spectroscopy and electrochemical study confirmed similar frontier molecular orbital levels of the three polymers in their solid state. More intriguingly, absorption profiles suggest that the sequence of side chains greatly governs the aggregation behaviors. Furthermore, the PTBI-2 film shows larger ordered domains than PTBI-1 and PTBI-3 films, as supported by AFM and GIWAXS measurements. As a result, PTBI-2-based FET devices achieved an average hole mobility of 1.37 cm2 V–1 s–1, much higher than the two polymers with other side-chain sequences. The regiorandom PTBI-3 exhibited the lowest average hole mobility of 0.27 cm2 V–1 s–1. This study highlights the significant impact of side-chain sequence regioisomerism on aggregation behaviors, morphologies, and subsequently charge transport properties of donor–acceptor type conjugated polymers.
DA - 2018/11/13/
PY - 2018/11/13/
DO - 10.1021/acs.macromol.8b01946
VL - 51
IS - 21
SP - 8486-8492
SN - 1520-5835
ER -
TY - JOUR
TI - Donor Conjugated Polymers with Polar Side Chain Groups: The Role of Dielectric Constant and Energetic Disorder on Photovoltaic Performance
AU - Xu, B.
AU - Yi, X.
AU - Huang, T.
AU - Zheng, Z.
AU - Zhang, J.
AU - Salehi, A.
AU - Coropceanu, V.
AU - Ho, C.H.Y.
AU - Marder, S.R.
AU - Toney, M.F.
AU - Brédas, J.-L.
AU - So, F.
AU - Reynolds, J.R.
T2 - Advanced Functional Materials
AB - Abstract To better understand the correlation of the dielectric properties with the photovoltaic response in conjugated polymer:fullerene bulk heterojunction materials, the concept of introducing minimal structural change is employed to increase the polymer dielectric constant via polar cyano groups added to the end of butyl or octyl side chains in the poly(dithienosilole‐thienopyrrolodione) system. Density functional theory calculations confirm that the polar groups do not affect the polymer electronic structure but can lead to an increase in overall dipole moment depending on the polymer chain conformation. Despite the increased dielectric constant (from 2.7 to 4.3 for cyano‐octyl side chains and from 2.7 to 3.2 for the cyano‐butyl analogues), the device characteristics employing the cyano‐containing polymers are inferior to those of the devices made with unfunctionalized alkyl chains. It is found that the hole mobilities for the cyano‐containing polymers are two orders of magnitude lower compared to those for the parent polymers and suggest this is due to an increase in energetic disorder caused by the strong local permanent dipoles associated with the cyano groups. The study highlights the complexity in the relationship between the dielectric constant of organic materials, the morphologies that are induced, and their photovoltaic performance.
DA - 2018///
PY - 2018///
DO - 10.1002/adfm.201803418
VL - 28
IS - 46
SP - 1803418
SN - 1616-3028
KW - conjugated polymers
KW - energetic disorder
KW - organic electronics
KW - organic solar cells
KW - photovoltaic devices
ER -
TY - JOUR
TI - A time-resolved millimeter wave conductivity (TR-mmWC) apparatus for charge dynamical properties of semiconductors
AU - Roy, Biswadev
AU - Jones, Charles R.
AU - Vlahovic, B.
AU - Ade, Harald W.
AU - Wu, Marvin H.
T2 - REVIEW OF SCIENTIFIC INSTRUMENTS
AB - This article demonstrates a contactless, time-resolved, millimeter wave conductivity apparatus capable of measuring photoconductivity of a diverse range of materials. This cavity-less system determines the time-dependent magnitude of a sample’s charge carrier density-mobility product by monitoring the response of a continuous, millimeter-wave probe beam following excitation of the sample by an ultrafast laser pulse. The probe beam is tunable from 110 GHz to 170 GHz and the sample response data can be obtained over the sub-nanosecond to millisecond time interval. This system has been tested on silicon wafers, S-I GaAs, perovskite thin films, SiO2-Ge(nc), and CdSxSe1−x nanowire samples. We demonstrate a minimum detectable photoconductance change of ∼1 µS, an estimated time resolution for conductance decay of ∼100 ps, and a dynamic range greater than 57 dB. The calibration constant of the system, needed for quantitative calculation of photoconductivity from experimental data, has been determined using silicon wafers. This system has several advantages over currently used microwave and terahertz techniques, such as facile tunability of probe frequency and substantially wider time range for study of decay kinetics, while maintaining an open sample environment that enables characterization of a wide range of sample sizes under controlled environmental conditions.
DA - 2018/10//
PY - 2018/10//
DO - 10.1063/1.5026848
VL - 89
IS - 10
SP -
SN - 1089-7623
UR - https://doi.org/10.1063/1.5026848
ER -
TY - JOUR
TI - The finale of a trilogy: comparing terpolymers and ternary blends with structurally similar backbones for use in organic bulk heterojunction solar cells
AU - Kelly, Mary Allison
AU - Zhang, Qianqian
AU - Peng, Zhengxing
AU - Noman, Victoria
AU - Zhu, Chenhui
AU - Ade, Harald
AU - You, Wei
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - Comparing the efficiency of terpolymers vs. ternary blends, this study focuses on two polymers with structurally similar backbones (monoCNTAZ and FTAZ) yet markedly different open circuit voltages.
DA - 2018/10/21/
PY - 2018/10/21/
DO - 10.1039/c8ta05132a
VL - 6
IS - 39
SP - 19190-19200
SN - 2050-7496
ER -
TY - JOUR
TI - Improvement of Photovoltaic Performance of Polymer Solar Cells by Rational Molecular Optimization of Organic Molecule Acceptors
AU - Li, Xiaojun
AU - Yao, Jia
AU - Angunawela, Indunil
AU - Sun, Chenkai
AU - Xue, Lingwei
AU - Liebman-Pelaez, Alexander
AU - Zhu, Chenhui
AU - Yang, Chunhe
AU - Zhang, Zhi-Guo
AU - Ade, Harald
AU - Li, Yongfang
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Two n‐type organic semiconductor (n‐OS) small molecules m ‐ITIC‐2F and m ‐ITIC‐4F with fluorinated 2‐(2,3‐dihydro‐3‐oxo‐1H‐inden‐1‐ylidene)propanedinitrile (IC) terminal moieties are prepared, for the application as an acceptor in polymer solar cells (PSCs), to further improve the photovoltaic performance of the n‐OS acceptor 3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene) indanone) ‐5,5,11,11‐tetrakis(3‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐sindaceno[1,2‐b:5,6‐b′]‐dithiophene ( m ‐ITIC). Compared to m ‐ITIC, these two new acceptors show redshifted absorption, higher molecular packing order, and improved electron mobilities. The power conversion efficiencies (PCE) of the as‐cast PSCs with m ‐ITIC‐2F or m ‐ITIC‐4F as an acceptor and a low‐cost donor–acceptor (D–A) copolymer PTQ10 as a donor reach 11.57% and 11.64%, respectively, which are among the highest efficiency for the as‐cast PSCs so far. Furthermore, after thermal annealing treatment, improved molecular packing and enhanced phase separation are observed, and the higher PCE of 12.53% is achieved for both PSCs based on the two acceptors. The respective and unique advantage with the intrinsic high degree of order, molecular packing, and electron mobilities of these two acceptors will be suitable to match with different p‐type organic semiconductor donors for higher PCE values, which provide a great potential for the PSCs commercialization in the near future. These results indicate that rational molecular structure optimization is of great importance to further improve photovoltaic properties of the photovoltaic materials.
DA - 2018/8/16/
PY - 2018/8/16/
DO - 10.1002/aenm.201800815
VL - 8
IS - 23
SP -
SN - 1614-6840
KW - molecular structure optimization
KW - n-type organic semiconductors
KW - organic molecule acceptors
KW - polymer solar cells
KW - power conversion efficiencies
ER -
TY - JOUR
TI - Effects of fused-ring regiochemistry on the properties and photovoltaic performance of n-type organic semiconductor acceptors
AU - Li, Xiaojun
AU - Huang, He
AU - Peng, Zhengxing
AU - Sun, Chenkai
AU - Yang, Dengchen
AU - Zhou, Jiadong
AU - Liebman-Pelaez, Alex
AU - Zhu, Chenhui
AU - Zhang, Zhi-Guo
AU - Zhang, Zhanjun
AU - Xie, Zengqi
AU - Ade, Harald
AU - Li, Yongfang
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - The effects of fused-ring regiochemistry on the physicochemical and photovoltaic properties of n-type organic semiconductor (n-OS) acceptors are investigated.
DA - 2018/9/7/
PY - 2018/9/7/
DO - 10.1039/c8ta05920a
VL - 6
IS - 33
SP - 15933-15941
SN - 2050-7496
ER -
TY - JOUR
TI - Effect of Side-Chain Engineering of Bithienylbenzodithiophene-alt-fluorobenzotriazole-Based Copolymers on the Thermal Stability and Photovoltaic Performance of Polymer Solar Cells
AU - Huang, He
AU - Bin, Haijun
AU - Peng, Zhengxing
AU - Qiu, Beibei
AU - Sun, Chenkai
AU - Liebman-Pelaez, Alex
AU - Zhang, Zhi-Guo
AU - Zhu, Chenhui
AU - Ade, Harald
AU - Zhang, Zhanjun
AU - Li, Yongfang
T2 - MACROMOLECULES
AB - Side-chain engineering of conjugated polymer donor materials is an important way for improving photovoltaic performances of polymer solar cells (PSCs). On the basis of the polymer J61 synthesized in our group, here, we design and synthesize three new 2D-conjugated polymers J62, J63, and J64 with different types of side chains to further investigate the effect of side chain on their physicochemical and photovoltaic properties. With the narrow bandgap n-type organic semiconductor (n-OS) ITIC as acceptor, the optimized PSCs based on polymer donor of J62 with linear octyl, J63 with linear unsaturated hexylene, and J64 with cyclohexane side chains display power conversion efficiency (PCE) of 10.81%, 8.13%, and 8.59%, respectively. After thermal treatment at 200 °C for 2 h on the active layer,the PCE of the PSC based on J63 still keeps 92% of the original value, which verifies that the cross-linking of the polymer can improve the thermal stability of PSCs. Morphological studies show that the active layer based on J63 displays strong lamellar packing with RMS 1.26, and the active layer based on J64 shows little phase separation with RMS 0.65. The RMS of the active layer based on J62 is 0.900, and the size of phase separation is between that of J63 and J64, which indicates the excessive high lamellar packing or low phase separation is harmful to the performance of PSCs. These results indicate that the side-chain engineering is an effective way to adjust the aggregation of polymers and the morphology of blend films, which are key factors to influence the performance of PSCs.
DA - 2018/8/14/
PY - 2018/8/14/
DO - 10.1021/acs.macromol.8b01036
VL - 51
IS - 15
SP - 6028-6036
SN - 1520-5835
ER -
TY - JOUR
TI - A Highly Crystalline Fused-Ring n-Type Small Molecule for Non-Fullerene Acceptor Based Organic Solar Cells and Field-Effect Transistors
AU - Song, Xin
AU - Gasparini, Nicola
AU - Nahid, Masrur Morshed
AU - Chen, Hu
AU - Macphee, Sky Marie
AU - Zhang, Weimin
AU - Norman, Victoria
AU - Zhu, Chenhui
AU - Bryant, Daniel
AU - Ade, Harald
AU - McCulloch, Iain
AU - Baran, Derya
T2 - ADVANCED FUNCTIONAL MATERIALS
AB - Abstract N‐type organic small molecules (SMs) are attracting attention in the organic electronics field, due to their easy purification procedures with high yield. However, only a few reports show SMs that perform well in both organic field‐effect transistors (OFETs) and organic solar cells (OSCs). Here, the synthesis and characterization of an n‐type small molecule with an indacenodithieno[3,2‐b]thiophene (IDTT) core unit and linear alkylated side chain (C 16 ) (IDTTIC) are reported. Compared to the state‐of‐the‐art n‐type molecule IDTIC, IDTTIC exhibits smaller optical bandgap and higher absorption coefficient, which is due to the enhanced intramolecular effect. After mixing with the polymer donor PBDB‐T, IDTIC‐based solar cells deliver a power conversion efficiency of only 5.67%. In stark contrast, the OSC performance of IDTTIC improves significantly to 11.2%. It is found that the superior photovoltaic properties of PBDB‐T:IDTTIC blends are mainly due to reduced trap‐assisted recombination and enhanced molecular packing coherence length and higher domain purity when compared to IDTIC. Moreover, a significantly higher electron mobility of 0.50 cm 2 V −1 s −1 for IDTTIC in OFET devices than for IDTIC (0.15 cm 2 V −1 s −1 ) is obtained. These superior performances in OSCs and OFETs demonstrate that SMs with extended π‐conjugation of the backbone possess a great potential for application in organic electronic devices.
DA - 2018/8/29/
PY - 2018/8/29/
DO - 10.1002/adfm.201802895
VL - 28
IS - 35
SP -
SN - 1616-3028
KW - fused-ring small molecules
KW - high photo-to-current efficiency
KW - non-fullerene acceptors
KW - organic field-effect transistors
KW - organic solar cells
ER -
TY - JOUR
TI - Miscibility-Function Relations in Organic Solar Cells: Significance of Optimal Miscibility in Relation to Percolation
AU - Ye, Long
AU - Collins, Brian A.
AU - Jiao, Xuechen
AU - Zhao, Jingbo
AU - Yan, He
AU - Ade, Harald
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Polymer solar cells (PSCs) continue to be a promising low‐cost and lead‐free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X‐ray microscopy method, the temperature dependences of “molecular miscibility” in the presence of fullerene crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high‐efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, an approach is outlined to convert liquidus miscibility to an effective Flory–Huggins interaction parameter χ. Crucially, determination of temperature‐dependent amorphous miscibility paves a way to rationally optimize the stability and mixing behaviors of PSCs at actual processing and operating temperatures.
DA - 2018/10/5/
PY - 2018/10/5/
DO - 10.1002/aenm.201703058
VL - 8
IS - 28
SP -
SN - 1614-6840
UR - https://doi.org/10.1002/aenm.201703058
KW - miscibility
KW - percolation thresholds
KW - polymer solar cells
KW - scanning transmission X-ray microscopy
ER -
TY - JOUR
TI - Carboxylate substitution position influencing polymer properties and enabling non-fullerene organic solar cells with high open circuit voltage and low voltage loss
AU - Liu, Jing
AU - Ma, Lik-Kuen
AU - Sheong, Fu Kit
AU - Zhang, Lin
AU - Hu, Huawei
AU - Zhang, Jing-Xuan
AU - Zhang, Jianquan
AU - Li, Zhengke
AU - Ma, Chao
AU - Han, Xu
AU - Pan, Ding
AU - Ade, Harald
AU - Ma, Wei
AU - Yan, He
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - A novel polymer P3TAE enables a high VOC of 1.20 V and a PCE of 8.10% for non-fullerene OSCs.
DA - 2018/9/21/
PY - 2018/9/21/
DO - 10.1039/c8ta04935a
VL - 6
IS - 35
SP - 16874-16881
SN - 2050-7496
ER -
TY - JOUR
TI - Effect of Ring-Fusion on Miscibility and Domain Purity: Key Factors Determining the Performance of PDI-Based Nonfullerene Organic Solar Cells
AU - Hu, Huawei
AU - Li, Yunke
AU - Zhang, Jianquan
AU - Peng, Zhengxing
AU - Ma, Lik-kuen
AU - Xin, Jingming
AU - Huang, Jiachen
AU - Ma, Tingxuan
AU - Jiang, Kui
AU - Zhang, Guangye
AU - Ma, Wei
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Compared to the rapid development of nonfullerene organic solar cells (OSCs) based on the state‐of‐the‐art indacenodithiophene (IDT)‐based small molecule acceptors (SMAs), the progress for perylene diimide (PDI)‐based electron acceptors has lagged behind owing to the lack of understanding on the structure–morphology–performance relationship of PDI SMAs. Given the ease of synthesis for PDIs and their high intrinsic electron mobility, it is crucial to identify key material parameters that influence the polymer:PDI blend morphology and to develop rational approaches for molecular design toward high‐performance PDI‐based SMAs. In this study, three pairs of PDI‐based SMAs with and without ring‐fusion are investigated and it is found that ring‐fusion and domain purity are the key structural and morphological factors determining the fill factors (FFs) and efficiencies of PDI‐based nonfullerene OSCs. This data shows that nonfullerene OSCs based on the ring‐fused PDI‐based SMAs exhibit much higher average domain purity and thus increased charge mobilities, which lead to enhanced FFs compared to those solar cells based on nonfused PDIs. This is explained by higher Florry Huggins interaction parameters as observed by melting point depression measurements. This study suggests that increasing repulsive molecular interactions to lower the miscibility between the polymer donor and PDI acceptor is the key to improve the FF and performance of PDI‐based devices.
DA - 2018/9/14/
PY - 2018/9/14/
DO - 10.1002/aenm.201800234
VL - 8
IS - 26
SP -
SN - 1614-6840
KW - average domain purity
KW - miscibility
KW - nonfullerene organic solar cells
KW - perylene diimide
KW - ring fusion
ER -
TY - JOUR
TI - Modulation of End Groups for Low-Bandgap Nonfullerene Acceptors Enabling High-Performance Organic Solar Cells
AU - Chen, Yuzhong
AU - Liu, Tao
AU - Hu, Huawei
AU - Ma, Tingxuan
AU - Lai, Joshua Yuk Lin
AU - Zhang, Jianquan
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract The field of nonfullerene organic solar cells (OSCs) has seen an impressive progress, largely due to advances in high‐performance small molecule acceptors (SMAs). As a large portion of the solar energy is located in the near‐infrared region, it is important to develop ultralow‐bandgap SMAs that have extended absorption in the spectral range of 800–1000 nm to maximize light absorption and efficiencies. In this work, three low‐bandgap SMAs, namely, IXIC, IXIC‐2Cl, and IXIC‐4Cl, are designed and synthesized with same fused terthieno[3,2‐ b ]thiophene donor unit and different end groups (EGs). The three SMAs all have low optical bandgap ( E g ) of 1.35, 1.30, and 1.25 eV, respectively. The chlorination on EGs can lower the energy level and broaden absorption range of the SMAs. As a result, the V oc of the devices is reduced but the J sc is significantly increased. In addition, the addition of chlorine atoms can enhance π–π stacking and crystallinity of the SMAs, which result in high fill factors. Overall, the optimum EGs are monochlorine‐substituted IC and OSCs based on PBDB‐T:IXIC‐2Cl that can achieve remarkable power conversion efficiencies (PCEs) of 12.2%, which is one of the highest PCEs for nonfullerene organic solar cells based on low‐bandgap SMAs.
DA - 2018/9/25/
PY - 2018/9/25/
DO - 10.1002/aenm.201801203
VL - 8
IS - 27
SP -
SN - 1614-6840
KW - end groups
KW - low-bandgap small molecule acceptors
KW - near-infrared
KW - organic solar cells
ER -
TY - JOUR
TI - Shear-Enhanced Transfer Printing of Conducting Polymer Thin Films
AU - Sen, Pratik
AU - Xiong, Yuan
AU - Zhang, Qanqian
AU - Park, Sungjune
AU - You, Wei
AU - Ade, Harald
AU - Kudenov, Michael W.
AU - Brendan T. O'Connor,
T2 - ACS APPLIED MATERIALS & INTERFACES
AB - Polymer conductors that are solution-processable provide an opportunity to realize low-cost organic electronics. However, coating sequential layers can be hindered by poor surface wetting or dissolution of underlying layers. This has led to the use of transfer printing where solid film inks are transferred from a donor substrate to partially fabricated devices using a stamp. This approach typically requires favorable adhesion differences between the stamp, ink, and receiving substrate. Here, we present a shear-assisted organic printing (SHARP) technique that employs a shear load on a post-less polydimethylsiloxane (PDMS) elastomer stamp to print large-area polymer films that can overcome large unfavorable adhesion differences between the stamp and receiving substrate. We explore the limits of this process by transfer printing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films with varied formulation that tune the adhesive fracture energy. Using this platform, we show that the SHARP process is able to overcome a 10-fold unfavorable adhesion differential without the use of a patterned PDMS stamp, enabling large-area printing. The SHARP approach is then used to print PEDOT:PSS films in the fabrication of high-performance semitransparent organic solar cells.
DA - 2018/9/19/
PY - 2018/9/19/
DO - 10.1021/acsami.8b09968
VL - 10
IS - 37
SP - 31560-31567
SN - 1944-8244
KW - transfer printing
KW - adhesion
KW - PEDOT:PSS
KW - surfactant
KW - organic photovoltaics
ER -
TY - JOUR
TI - Sub-Band Gap Turn-On Near-Infrared-to-Visible Up-Conversion Device Enabled by an Organic?Inorganic Hybrid Perovskite Photovoltaic Absorber
AU - Yu, Hyeonggeun
AU - Cheng, Yuanhang
AU - Li, Menglin
AU - Tsang, Sai-Wing
AU - So, Franky
T2 - ACS APPLIED MATERIALS & INTERFACES
AB - Direct integration of an infrared (IR) photodetector with an organic light-emitting diode (OLED) enables low-cost, pixel-free IR imaging. However, the operation voltage of the resulting IR-to-visible up-conversion is large because of the series device architecture. Here, we report a low-voltage near-IR (NIR)-to-visible up-conversion device using formamidinium lead iodide as a NIR absorber integrated with a phosphorescent OLED. Because of the efficient photocarrier injection from the hybrid perovskite layer to the OLED, we observed a sub-band gap turn-on of the OLED under NIR illumination. The device showed a NIR-to-visible up-conversion efficiency of 3% and a luminance on/off ratio of 103 at only 5 V. Finally, we demonstrate pixel-free NIR imaging using the up-conversion device.
DA - 2018/5/9/
PY - 2018/5/9/
DO - 10.1021/acsami.8b00592
VL - 10
IS - 18
SP - 15920-15925
SN - 1944-8244
KW - organo-halide perovskite
KW - infrared imaging
KW - up-conversion
KW - organic light-emitting diode
KW - photovoltaic
ER -
TY - JOUR
TI - Molecular engineering of perylene-diimide-based polymer acceptors containing heteroacene units for all-polymer solar cells
AU - Suranagi, Sanjaykumar R.
AU - Singh, Ranbir
AU - Kim, Joo-Hyun
AU - Kim, Min
AU - Ade, Harald
AU - Cho, Kilwon
T2 - ORGANIC ELECTRONICS
AB - Polymer acceptors based on perylene diimide (PDI) with three symmetrical S-heteroacene backbone units of different sizes were synthesized for use in all-polymer solar cells (all-PSCs). The effects of varying the size of the heteroacene unit on the backbone of the PDI polymer are evident in the absorption spectra and their energy level offsets, which are correlated with their morphological and photovoltaic properties. These newly synthesized polymers were employed as acceptors with the polymer poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c]-[1,2,5]thiadiazole)] (PPDT2FBT) as the donor in all-PSCs that were found to exhibit modest power conversion efficiencies. The variations in photovoltaic properties of all-PSCs are investigated by characterizing the charge generation, carrier mobilities and recombination. The morphological disorder at the polymer/PPDT2FBT interface and average composition variations are revealed by using grazing incidence wide angle X-ray scattering (GIWAXS) and resonance soft X-ray scattering (R-SoXS) characterizations.
DA - 2018/7//
PY - 2018/7//
DO - 10.1016/j.orgel.2018.02.015
VL - 58
SP - 222-230
SN - 1878-5530
KW - Perylene-diimide
KW - All-polymer solar cell
KW - Bulk-heterojunction
KW - Resonance soft X-ray scattering
ER -
TY - JOUR
TI - High-Efficiency All-Small-Molecule Organic Solar Cells Based on an Organic Molecule Donor with Alkylsilyl-Thienyl Conjugated Side Chains
AU - Bin, Haijun
AU - Yao, Jia
AU - Yang, Yankang
AU - Angunawela, Indunil
AU - Sun, Chenkai
AU - Gao, Liang
AU - Ye, Long
AU - Qiu, Beibei
AU - Xue, Lingwei
AU - Zhu, Chenhui
AU - Yang, Chunhe
AU - Zhang, Zhi-Guo
AU - Ade, Harald
AU - Li, Yongfang
T2 - ADVANCED MATERIALS
AB - Abstract Two medium‐bandgap p‐type organic small molecules H21 and H22 with an alkylsily‐thienyl conjugated side chain on benzo[1,2‐ b :4,5‐ b ′]dithiophene central units are synthesized and used as donors in all‐small‐molecule organic solar cells (SM‐OSCs) with a narrow‐bandgap n‐type small molecule 2,2′‐((2Z,2′Z)‐((4,4,9,9‐tetrahexyl‐4,9‐dihydro‐ s ‐indaceno[1,2‐ b :5,6‐ b ′]dithiophene‐2,7‐diyl)bis(methanylylidene))bis(3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (IDIC) as the acceptor. In comparison to H21 with 3‐ethyl rhodanine as the terminal group, H22 with cyanoacetic acid esters as the terminal group shows blueshifted absorption, higher charge‐carrier mobility and better 3D charge pathway in blend films. The power conversion efficiency (PCE) of the SM‐OSCs based on H22:IDIC reaches 10.29% with a higher open‐circuit voltage of 0.942 V and a higher fill factor of 71.15%. The PCE of 10.29% is among the top efficiencies of nonfullerene SM‐OSCs reported in the literature to date.
DA - 2018/7/5/
PY - 2018/7/5/
DO - 10.1002/adma.201706361
VL - 30
IS - 27
SP -
SN - 1521-4095
KW - alkylsilyl-thienyl conjugated side-chains
KW - organic small-molecule donor materials
KW - organic solar cells
ER -
TY - JOUR
TI - Flexoelectricity in a metal/ferroelectric/semiconductor heterostructure
AU - Huang, Shujin
AU - Yau, Hei-Man
AU - Yu, Hyeonggeun
AU - Qi, Lu
AU - So, Franky
AU - Dai, Ji-Yan
AU - Jiang, Xiaoning
T2 - AIP ADVANCES
AB - The flexoelectricity in a 100 nm-thick BaTiO3 (BTO) thin film based metal/ferroelectric insulator/semiconductor (MFS) heterostructure was reported in this letter. The transverse flexoelectric coefficient of the BTO thin film in the heterojunction structure was measured to be 287-418 μC/m at room temperature, and its temperature dependence shows that the flexoelectric effect in the BTO thin film was dominated in the paraelectric phase. We showed that the BTO thin film capacitance could be controlled at multi-levels by introducing ferroelectric and flexoelectric polarization in the film. These results are promising for understanding of the flexoelectricity in epitaxial ferroelectric thin films and practical applications of the enhanced flexoelectricity in nanoscale devices.
DA - 2018/6//
PY - 2018/6//
DO - 10.1063/1.5031162
VL - 8
IS - 6
SP -
SN - 2158-3226
ER -
TY - JOUR
TI - Every Atom Counts: Elucidating the Fundamental Impact of Structural Change in Conjugated Polymers for Organic Photovoltaics
AU - Lo, Chi Kin
AU - Gautam, Bhoj R.
AU - Selter, Philipp
AU - Zheng, Zilong
AU - Oosterhout, Stefan D.
AU - Constantinou, Iordania
AU - Knitsch, Robert
AU - Wolfe, Rylan M. W.
AU - Yi, Xueping
AU - Bredas, Jean-Luc
AU - So, Franky
AU - Toney, Michael F.
AU - Coropceanu, Veaceslav
AU - Hansen, Michael Ryan
AU - Gundogdu, Kenan
AU - Reynolds, John R.
T2 - CHEMISTRY OF MATERIALS
AB - As many conjugated polymer-based organic photovoltaic (OPV) materials provide substantial solar power conversion efficiencies (as high as 13%), it is important to develop a deeper understanding of how the primary repeat unit structures impact device performance. In this work, we have varied the group 14 atom (C, Si, Ge) at the center of a bithiophene fused ring to elucidate the impact of a minimal repeat unit structure change on the optical, transport, and morphological properties, which ultimately control device performance. Careful polymerization and polymer purification produced three “one-atom change” donor–acceptor conjugated alternating copolymers with similar molecular weights and dispersities. DFT calculation, absorption spectroscopy, and high-temperature solution 1H nuclear magnetic resonance (NMR) results indicate that poly(dithienosilole-alt-thienopyrrolodione), P(DTS-TPD), and poly(dithienogermole-alt-thienopyrrolodione), P(DTG-TPD) exhibit different rotational conformations when compared to poly(cyclopentadithiophene-alt-thienopyrrolodione), P(DTC-TPD). Solid-state 1H MAS NMR experiments reveal that the greater probability of the anticonformation in P(DTS-TPD) and P(DTG-TPD) prevail in the solid phase. The conformational variation seen in solution and solid-state NMR in turn affects the polymer stacking and intermolecular interaction. Two-dimension 1H-1H DQ-SQ NMR correlation spectra shows aromatic–aromatic correlations for P(DTS-TPD) and P(DTG-TPD), which on the other hand is absent for P(DTC-TPD). In a thin-film interchain packing study using grazing incidence wide-angle X-ray scattering (GIWAXS), we observe the π-face of the conjugated backbones of P(DTC-TPD) aligned edge-on to the substrate, whereas in contrast the π-faces of P(DTS-TPD) and P(DTG-TPD) align parallel to the surface. These differences in polymer conformations and backbone orientations lead to variations in the OPV performance of blends with the fullerene PC71BM, with the device containing P(DTC-TPD):PCBM having a lower fill factor and a lower power conversion efficiency. Ultrafast transient absorption spectroscopy shows the P(DTC-TPD):PCBM blend to have a more pronounced triplet formation from bimolecular recombination of initially separated charges. With a combination of sub-bandgap external quantum efficiency measurements and DFT calculations, we present evidence that the greater charge recombination loss is the result of a lower lying triplet energy level for P(DTC-TPD), leading to a higher rate of recombination and lower OPV device performance. Importantly, this study ties ultimate photovoltaic performance to morphological features in the active films that are induced from the processing solution and are a result of minimal one-atom differences in polymer repeat unit structure.
DA - 2018/5/8/
PY - 2018/5/8/
DO - 10.1021/acs.chemmater.8b00590
VL - 30
IS - 9
SP - 2995-3009
SN - 1520-5002
ER -
TY - JOUR
TI - A Wide Band Gap Polymer with a Deep Highest Occupied Molecular Orbital Level Enables 14.2% Efficiency in Polymer Solar Cells
AU - Li, Sunsun
AU - Ye, Long
AU - Zhao, Wenchao
AU - Yan, Hongping
AU - Yang, Bei
AU - Liu, Delong
AU - Li, Wanning
AU - Ade, Harald
AU - Hou, Jianhui
T2 - JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
AB - To simultaneously achieve low photon energy loss (Eloss) and broad spectral response, the molecular design of the wide band gap (WBG) donor polymer with a deep HOMO level is of critical importance in fullerene-free polymer solar cells (PSCs). Herein, we developed a new benzodithiophene unit, i.e., DTBDT-EF, and conducted systematic investigations on a WBG DTBDT-EF-based donor polymer, namely, PDTB-EF-T. Due to the synergistic electron-withdrawing effect of the fluorine atom and ester group, PDTB-EF-T exhibits a higher oxidation potential, i.e., a deeper HOMO level (ca. −5.5 eV) than most well-known donor polymers. Hence, a high open-circuit voltage of 0.90 V was obtained when paired with a fluorinated small molecule acceptor (IT-4F), corresponding to a low Eloss of 0.62 eV. Furthermore, side-chain engineering demonstrated that subtle side-chain modulation of the ester greatly influences the aggregation effects and molecular packing of polymer PDTB-EF-T. With the benefits of the stronger interchain π–π interaction, the improved ordering structure, and thus the highest hole mobility, the most symmetric charge transport and reduced recombination are achieved for the linear decyl-substituted PDTB-EF-T (P2)-based PSCs, leading to the highest short-circuit current density and fill factor (FF). Due to the high Flory–Huggins interaction parameter (χ), surface-directed phase separation occurs in the P2:IT-4F blend, which is supported by X-ray photoemission spectroscopy results and cross-sectional transmission electron microscope images. By taking advantage of the vertical phase distribution of the P2:IT-4F blend, a high power conversion efficiency (PCE) of 14.2% with an outstanding FF of 0.76 was recorded for inverted devices. These results demonstrate the great potential of the DTBDT-EF unit for future organic photovoltaic applications.
DA - 2018/6/13/
PY - 2018/6/13/
DO - 10.1021/jacs.8b02695
VL - 140
IS - 23
SP - 7159-7167
SN - 0002-7863
ER -
TY - JOUR
TI - Multiple Cases of Efficient Nonfullerene Ternary Organic Solar Cells Enabled by an Effective Morphology Control Method
AU - Jiang, Kui
AU - Zhang, Guangye
AU - Yang, Guofang
AU - Zhang, Jianquan
AU - Li, Zhengke
AU - Ma, Tingxuan
AU - Hu, Huawei
AU - Ma, Wei
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Ternary organic solar cells (OSCs) have attracted much research attention, as they can maintain the simplicity of the single‐junction device architecture while broadening the absorption range of OSCs. However, one main challenge that limits the development of ternary OSCs is the difficulty in controlling the morphology of ternary OSCs. In this paper, an effective approach to control the morphology is presented that leads to multiple cases of efficient nonfullerene ternary OSCs with efficiencies of up to 11.2%. This approach is based on a donor polymer with strong temperature dependent aggregation properties processed from hot solutions without any solvent additives and a pair of small molecular acceptors (SMAs) that have similar surface tensions and thus low propensity to form discrete phases. Such a ternary blend exhibits a simplified bulk‐heterojunction morphology that is similar to the morphology of previously reported binary blends. As a result, an almost linear relationship between V OC and film composition is observed for all nonfullerene ternary devices. Meanwhile, by carefully designing a control system with a large interfacial tension, a different phase separation and V OC dependence is demonstrated. This morphology control approach can be applicable to more material systems and accelerates the development of the ternary OSC field.
DA - 2018/3/26/
PY - 2018/3/26/
DO - 10.1002/aenm.201701370
VL - 8
IS - 9
SP -
SN - 1614-6840
UR - https://doi.org/10.1002/aenm.201701370
KW - morphology
KW - non-fullerene
KW - organic solar cells
KW - photovoltaics
KW - surface tension
KW - small molecular acceptors
KW - ternary blends
ER -
TY - JOUR
TI - Measuring Temperature-Dependent Miscibility for Polymer Solar Cell Blends: An Easily Accessible Optical Method Reveals Complex Behavior
AU - Peng, Zhengxing
AU - Jiao, Xuechen
AU - Ye, Long
AU - Li, Sunsun
AU - Rech, Jeromy James
AU - You, Wei
AU - Hou, Jianhui
AU - Ade, Harald
T2 - CHEMISTRY OF MATERIALS
AB - In bulk-heterojunction polymer solar cells (PSC), the molecular-level mixing between conjugated polymer donors and small-molecule acceptors plays a crucial role in obtaining a desirable morphology and good device stability. It has been recently shown that the thermodynamic limit of this mixing can be quantified by the liquidus miscibility, the composition of the small-molecule acceptor in amorphous phases in the presence of small-molecule crystals, and then converted to the Flory–Huggins interaction parameter χ. This conversion maps out the amorphous miscibility. Moreover, the quantitative relations between χ and the fill factor of PSC devices were established recently. However, the commonly used measurement of this liquidus miscibility, scanning transmission X-ray microscopy, is not easily and readily accessible. Here, we delineate a method based on common visible light microscopy and ultraviolet–visible absorption spectroscopy to replace the X-ray measurements. To demonstrate the feasibility of this technique and methodology, a variety of conjugated polymers (PffBT4T-C9C13, PDPP3T PBDT-TS1, PTB7-Th, and FTAZ) and their miscibility with fullerenes or nonfullerene small molecules (PC71BM, PC61BM, and EH-IDTBR) are characterized. The establishment of this methodology will pave the way to a wider use of the liquidus miscibility and the critical miscibility-function relations to optimize the device performance and obtain good stability in PSCs and other devices.
DA - 2018/6/26/
PY - 2018/6/26/
DO - 10.1021/acs.chemmater.8b00889
VL - 30
IS - 12
SP - 3943-3951
SN - 1520-5002
ER -
TY - JOUR
TI - Alkyl Chain Regiochemistry of Benzotriazole-Based Donor Polymers Influencing Morphology and Performances of Non-Fullerene Organic Solar Cells
AU - Chen, Shangshang
AU - Zhang, Lin
AU - Ma, Chao
AU - Meng, Dong
AU - Zhang, Jianquan
AU - Zhang, Guangye
AU - Li, Zhengke
AU - Chow, Philip C. Y.
AU - Ma, Wei
AU - Wang, Zhaohui
AU - Wong, Kam Sing
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract The effects of alkyl chain regiochemistry on the properties of donor polymers and performances of non‐fullerene organic solar cells are investigated. Two donor polymers (PfBTAZ and PfBTAZS) are compared that have nearly identical chemical structures except for the regiochemistry of alkyl chains. The optical properties and crystallinity of two polymers are nearly identical yet the PfBTAZ:O‐IDTBR blend exhibits nearly double domain size compared to the blend based on PfBTAZS:O‐IDTBR. To reveal the origins of the very different domain size of two blends, the morphology of neat polymer films is characterized, and it is found that PfBTAZ tends to aggregate into much larger polymer fibers without the presence of O‐IDTBR. This indicates that it is not the polymer:O‐IDTBR interactions but the intrinsic aggregation properties of two polymers that determine the morphology features of neat and blend films. The stronger aggregation tendency of PfBTAZ could be explained by its more co‐planar geometry of the polymer backbone arising from the different alkyl chain regiochemistry. Combined with the similar trend observed in another set of donor polymers (PTFB‐P and PTFB‐PS), the results provide an important understanding of the structure–property relationships that could guide the development of donor polymers for non‐fullerene organic solar cells.
DA - 2018/4/16/
PY - 2018/4/16/
DO - 10.1002/aenm.201702427
VL - 8
IS - 11
SP -
SN - 1614-6840
KW - alkyl chains
KW - morphology
KW - organic solar cells
KW - small-molecular acceptors
ER -
TY - JOUR
TI - A High-Efficiency Organic Solar Cell Enabled by the Strong Intramolecular Electron Push-Pull Effect of the Nonfullerene Acceptor
AU - Li, Wanning
AU - Ye, Long
AU - Li, Sunsun
AU - Yao, Huifeng
AU - Ade, Harald
AU - Hou, Jianhui
T2 - ADVANCED MATERIALS
AB - Besides broadening of the absorption spectrum, modulating molecular energy levels, and other well-studied properties, a stronger intramolecular electron push-pull effect also affords other advantages in nonfullerene acceptors. A strong push-pull effect improves the dipole moment of the wings in IT-4F over IT-M and results in a lower miscibility than IT-M when blended with PBDB-TF. This feature leads to higher domain purity in the PBDB-TF:IT-4F blend and makes a contribution to the better photovoltaic performance. Moreover, the strong push-pull effect also decreases the vibrational relaxation, which makes IT-4F more promising than IT-M in reducing the energetic loss of organic solar cells. Above all, a power conversion efficiency of 13.7% is recorded in PBDB-TF:IT-4F-based devices.
DA - 2018/4/19/
PY - 2018/4/19/
DO - 10.1002/adma.201707170
VL - 30
IS - 16
SP -
SN - 1521-4095
KW - intramolecular electron push-pull effect
KW - miscibility
KW - nonfullerene acceptor
KW - organic solar cell
KW - vibrational relaxation
ER -
TY - JOUR
TI - The Role of FRET in Non-Fullerene Organic Solar Cells: Implications for Molecular Design
AU - Gautam, Bhoj R.
AU - Younts, Robert
AU - Carpenter, Joshua
AU - Ade, Harald
AU - Gundogdu, Kenan
T2 - JOURNAL OF PHYSICAL CHEMISTRY A
AB - Non-fullerene acceptors (NFAs) have been demonstrated to be promising candidates for highly efficient organic photovoltaic (OPV) devices. The tunability of absorption characteristics of NFAs can be used to make OPVs with complementary donor–acceptor absorption to cover a broad range of the solar spectrum. However, both charge transfer from donor to acceptor moieties and energy (energy) transfer from high-bandgap to low-bandgap materials are possible in such structures. Here, we show that when charge transfer and exciton transfer processes are both present, the coexistence of excitons in both domains can cause a loss mechanism. Charge separation of excitons in a low-bandgap material is hindered due to exciton population in the larger bandgap acceptor domains. Our results further show that excitons in low-bandgap material should have a relatively long lifetime compared to the transfer time of excitons from higher bandgap material in order to contribute to the charge separation. These observations provide significant guidance for design and development of new materials in OPV applications.
DA - 2018/4/19/
PY - 2018/4/19/
DO - 10.1021/acs.jpca.7b12807
VL - 122
IS - 15
SP - 3764-3771
SN - 1089-5639
ER -
TY - JOUR
TI - Polymer non-fullerene solar cells of vastly different efficiencies for minor side-chain modification: impact of charge transfer, carrier lifetime, morphology and mobility
AU - Awartani, Omar M.
AU - Gautam, Bhoj
AU - Zhao, Wenchao
AU - Younts, Robert
AU - Hou, Jianhui
AU - Gundogdu, Kenan
AU - Ade, Harald
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - The performance of the 11.25% efficient PBDB-T : ITIC system degraded to 4.35% after a minor side-chain modification in PBDB-O : ITIC. In this study, the underlying reasons behind this vast difference in efficiencies are investigated.
DA - 2018/7/14/
PY - 2018/7/14/
DO - 10.1039/c7ta01746d
VL - 6
IS - 26
SP - 12484-12492
SN - 2050-7496
UR - https://doi.org/10.1039/C7TA01746D
ER -
TY - JOUR
TI - Langmuir-Blodgett Thin Films of Diketopyrrolopyrrole-Based Amphiphiles
AU - Lo, Chi Kin
AU - Wang, Cheng-Yin
AU - Oosterhout, Stefan D.
AU - Zheng, Zilong
AU - Yi, Xueping
AU - Fuentes-Hernandez, Canek
AU - So, Franky
AU - Coropceanu, Veaceslav
AU - Bredas, Jean-Luc
AU - Toney, Michael F.
AU - Kippelen, Bernard
AU - Reynolds, John R.
T2 - ACS APPLIED MATERIALS & INTERFACES
AB - We report on two π-conjugated donor–acceptor–donor (D–A–D) molecules of amphiphilic nature, aiming to promote intermolecular ordering and carrier mobility in organic electronic devices. Diketopyrrolopyrrole was selected as the acceptor moiety that was disubstituted with nonpolar and polar functional groups, thereby providing the amphiphilic structures. This structural design resulted in materials with a strong intermolecular order in the solid state, which was confirmed by differential scanning calorimetry and polarized optical microscopy. Langmuir–Blodgett (LB) films of ordered mono- and multilayers were transferred onto glass and silicon substrates, with layer quality, coverage, and intermolecular order controlled by layer compression pressure on the LB trough. Organic field-effect transistors and organic photovoltaics devices with active layers consisting of the amphiphilic conjugated D–A–D-type molecules were constructed to demonstrate that the LB technique is an effective layer-by-layer deposition approach to fabricate self-assembled, ordered thin films.
DA - 2018/4/11/
PY - 2018/4/11/
DO - 10.1021/acsami.7b18239
VL - 10
IS - 14
SP - 11995-12004
SN - 1944-8252
KW - Langmuir-Blodgett
KW - monolayer
KW - amphiphilic molecules
KW - diketopyrrolopyrrole
KW - layer-by-layer deposition
KW - organic field-effect transistor
KW - donor-acceptor-donor molecules
ER -
TY - JOUR
TI - A polymer design strategy toward green solvent processed efficient non-fullerene polymer solar cells
AU - Qin, Yunpeng
AU - Ye, Long
AU - Zhang, Shaoqing
AU - Zhu, Jie
AU - Yang, Bei
AU - Ade, Harald
AU - Hou, Jianhui
T2 - JOURNAL OF MATERIALS CHEMISTRY A
AB - This work suggests an effective material design strategy to prepare efficient PSCs with a green solvent, which is important in PSCs.
DA - 2018/3/14/
PY - 2018/3/14/
DO - 10.1039/c8ta00368h
VL - 6
IS - 10
SP - 4324-4330
SN - 2050-7496
ER -
TY - JOUR
TI - Quantitative relations between interaction parameter, miscibility and function in organic solar cells
AU - Ye, Long
AU - Hu, Huawei
AU - Ghasemi, Masoud
AU - Wang, Tonghui
AU - Collins, Brian A.
AU - Kim, Joo-Hyun
AU - Jiang, Kui
AU - Carpenter, Joshua H.
AU - Li, Hong
AU - Li, Zhengke
AU - McAfee, Terry
AU - Zhao, Jingbo
AU - Chen, Xiankai
AU - Lai, Joshua Lin Yuk
AU - Ma, Tingxuan
AU - Bredas, Jean-Luc
AU - Yan, He
AU - Ade, Harald
T2 - NATURE MATERIALS
DA - 2018/3//
PY - 2018/3//
DO - 10.1038/s41563-017-0005-1
VL - 17
IS - 3
SP - 253-260
SN - 1476-4660
ER -
TY - JOUR
TI - Manipulating Refractive Index in Organic Light-Emitting Diodes
AU - Salehi, Amin
AU - Chen, Ying
AU - Fu, Xiangyu
AU - Peng, Cheng
AU - So, Franky
T2 - ACS APPLIED MATERIALS & INTERFACES
AB - In a conventional organic light-emitting diode (OLED), only a fraction of light can escape to the glass substrate and air. Most radiation is lost to two major channels: waveguide modes and surface plasmon polaritons. It is known that reducing the refractive indices of the constituent layers in an OLED can enhance light extraction. Among all of the layers, the refractive index of the electron transport layer (ETL) has the largest impact on light extraction because it is the layer adjacent to the metallic cathode. Oblique angle deposition (OAD) provides a way to manipulate the refractive index of a thin film by creating an ordered columnar void structure. In this work, using OAD, the refractive index of tris(8-hydroxyquinoline)aluminum (Alq3) can be tuned from 1.75 to 1.45. With this low-index ETL deposited by OAD, the resulting phosphorescent OLED shows nearly 30% increase in light extraction efficiency.
DA - 2018/3/21/
PY - 2018/3/21/
DO - 10.1021/acsami.7b18514
VL - 10
IS - 11
SP - 9595-9601
SN - 1944-8244
KW - organic light-emitting diodes
KW - oblique angle deposition
KW - spectroscopic ellipsometry
KW - refractive index
KW - electron transport layer
ER -
TY - JOUR
TI - Integrated circuits based on conjugated polymer monolayer
AU - Li, Mengmeng
AU - Mangalore, Deepthi Kamath
AU - Zhao, Jingbo
AU - Carpenter, Joshua H.
AU - Yan, Hongping
AU - Ade, Harald
AU - Yan, He
AU - Muellen, Klaus
AU - Blom, Paul W. M.
AU - Pisula, Wojciech
AU - Leeuw, Dago M.
AU - Asadi, Kamal
T2 - NATURE COMMUNICATIONS
AB - It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm2 V-1 s-1. The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.
DA - 2018/1/31/
PY - 2018/1/31/
DO - 10.1038/s41467-017-02805-5
VL - 9
SP -
SN - 2041-1723
ER -
TY - JOUR
TI - Surpassing 10% efficiency benchmark for nonfullerene organic solar cells by scalable coating in air from single nonhalogenated solvent
AU - Ye, Long
AU - Xiong, Y.
AU - Zhang, Q. Q.
AU - Li, S. S.
AU - Wang, C.
AU - Jiang, Z.
AU - Hou, J. H.
AU - You, W.
AU - Ade, Harald
T2 - Advanced Materials
AB - Realizing over 10% efficiency in printed organic solar cells via scalable materials and less toxic solvents remains a grand challenge. In article number 1705485, Harald Ade and co-workers report chlorine-free, in-air blade-coating of a new photoactive combination, FTAZ:IT-M, which is able to yield an efficiency of nearly 11%, despite a high humidity of ≈50%.
DA - 2018///
PY - 2018///
DO - 10.1002/adma.201870054
VL - 30
IS - 8
ER -
TY - JOUR
TI - Influence of Donor Polymer on the Molecular Ordering of Small Molecular Acceptors in Nonfullerene Polymer Solar Cells
AU - Hu, Huawei
AU - Jiang, Kui
AU - Chow, Philip C. Y.
AU - Ye, Long
AU - Zhang, Guangye
AU - Li, Zhengke
AU - Carpenter, Joshua H.
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Nonfullerene polymer solar cells (PSCs) based on polymer donors and nonfullerene small molecular acceptors (SMAs) have recently attracted considerable attention. Although much of the progress is driven by the development of novel SMAs, the donor polymer also plays an important role in achieving efficient nonfullerene PSCs. However, it is far from clear how the polymer donor choice influences the morphology and performance of the SMAs and the nonfullerene blends. In addition, it is challenging to carry out quantitative analysis of the morphology of polymer:SMA blends, due to the low material contrast and overlapping scattering features of the π–π stacking between the two organic components. Here, a series of nonfullerene blends is studied based on ITIC‐Th blended with five different donor polymers. Through quantitative morphology analysis, the (010) coherence length of the SMA is characterized and a positive correlation between the coherence length of the SMA and the device fill factor (FF) is established. The study reveals that the donor polymer can significantly change the molecular ordering of the SMA and thus improve the electron mobility and domain purity of the blend, which has an overall positive effect that leads to the enhanced device FF for nonfullerene PSCs.
DA - 2018/2/15/
PY - 2018/2/15/
DO - 10.1002/aenm.201701674
VL - 8
IS - 5
SP -
SN - 1614-6840
KW - coherence length
KW - morphology
KW - polymer solar cells
KW - small molecular acceptor
KW - X-ray scattering
ER -
TY - JOUR
TI - High-Performance Wide Bandgap Copolymers Using an EDOT Modified Benzodithiophene Donor Block with 10.11% Efficiency
AU - Feng, Kui
AU - Yang, Guofang
AU - Xu, Xiaopeng
AU - Zhang, Guangjun
AU - Yan, He
AU - Awartani, Omar
AU - Ye, Long
AU - Ade, Harald
AU - Li, Ying
AU - Peng, Qiang
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Newly developed benzo[1,2‐b:4,5‐b′]dithiophene (BDT) block with 3,4‐ethylenedioxythiophene (EDOT) side chains is first employed to build efficient photovoltaic copolymers. The resulting copolymers, PBDTEDOT‐BT and PBDTEDOTFBT, have a large bandgap more than 1.80 eV, which is attributed to the increased steric hindrance between the BDT and EDOT skeletons. Both copolymers possess the satisfied absorptions, low‐lying highest occupied molecular orbital (HOMO) levels and high crystallinity. Using the fluorination strategy, PBDTEDOT‐FBT exhibits a wider and stronger absorption and a deeper HOMO level than those of PBDTEDOT‐BT. PBDTEDOT‐FBT:[6,6]‐Phenyl C 71 butyric acid methyl ester (PC 71 BM) blend also shows the higher hole mobility and better surface morphology compared with the PBDTEDOTBT:PC 71 BM blend. Combination of above advantages, PBDTEDOT‐FBT devices exhibit much higher power conversion efficiency (PCE) of 10.11%, with an improved open circuit voltage (V oc ) of 0.86 V, short circuit current densities (J sc ) of 16.01 mA cm −2 , and fill factor (FF) of 72.6%. This work not only provides a newly efficient candidate of BDT donor block modified with EDOT conjugated side chains, but also achieves high‐performance large bandgap copolymers for polymer solar cells (PSCs) via the synergistic effect of fluorination and side chain engineering strategies.
DA - 2018/2/26/
PY - 2018/2/26/
DO - 10.1002/aenm.201602773
VL - 8
IS - 6
SP -
SN - 1614-6840
KW - ethylenedioxythiophene (EDOT)
KW - fluorination
KW - polymer solar cells
KW - side chain engineering
KW - wide bandgap copolymers
ER -
TY - JOUR
TI - Charge Generation and Recombination in an Organic Solar Cell with Low Energetic Offsets
AU - Ran, Niva A.
AU - Love, John A.
AU - Heiber, Michael C.
AU - Jiao, Xuechen
AU - Hughes, Michael P.
AU - Karki, Akchheta
AU - Wang, Ming
AU - Brus, Viktor V.
AU - Wang, Hengbin
AU - Neher, Dieter
AU - Ade, Harald
AU - Bazan, Guillermo C.
AU - Nguyen, Thuc-Quyen
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract Organic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short‐circuit currents ( J SC ) and fill factors ( FF ). However, it is necessary to reduce the energetic offsets to achieve high open‐circuit voltages ( V OC ). Recently, reports have highlighted BHJ blends that are pushing at the accepted limits of energetic offsets necessary for high efficiency. Unfortunately, most of these BHJs have modest FF values. How the energetic offset impacts the solar cell characteristics thus remains poorly understood. Here, a comprehensive characterization of the losses in a polymer:fullerene BHJ blend, PIPCP:phenyl‐C61‐butyric acid methyl ester (PC 61 BM), that achieves a high V OC (0.9 V) with very low energy losses ( E loss = 0.52 eV) from the energy of absorbed photons, a respectable J SC (13 mA cm −2 ), but a limited FF (54%) is reported. Despite the low energetic offset, the system does not suffer from field‐dependent generation and instead it is characterized by very fast nongeminate recombination and the presence of shallow traps. The charge‐carrier losses are attributed to suboptimal morphology due to high miscibility between PIPCP and PC 61 BM. These results hold promise that given the appropriate morphology, the J SC , V OC , and FF can all be improved, even with very low energetic offsets.
DA - 2018/2/15/
PY - 2018/2/15/
DO - 10.1002/aenm.201701073
VL - 8
IS - 5
SP -
SN - 1614-6840
KW - energetic offset
KW - fill factor
KW - morphology
KW - organic solar cells
KW - recombination
ER -
TY - JOUR
TI - A Facile Method to Fine-Tune Polymer Aggregation Properties and Blend Morphology of Polymer Solar Cells Using Donor Polymers with Randomly Distributed Alkyl Chains
AU - Yao, Huatong
AU - Li, Yunke
AU - Hu, Huawei
AU - Chow, Philip C. Y.
AU - Chen, Shangshang
AU - Zhao, Jingbo
AU - Li, Zhengke
AU - Carpenter, Joshua H.
AU - Lai, Joshua Yuk Lin
AU - Yang, Guofang
AU - Liu, Yuhang
AU - Lin, Haoran
AU - Ade, Harald
AU - Yan, He
T2 - ADVANCED ENERGY MATERIALS
AB - Abstract The device performance of polymer solar cells (PSCs) is strongly dependent on the blend morphology. One of the strategies for improving PSC performance is side‐chain engineering, which plays an important role in controlling the aggregation properties of the polymers and thus the domain crystallinity/purity of the donor–acceptor blends. In particular, for a family of high‐performance donor polymers with strong temperature‐dependent aggregation properties, the device performances are very sensitive to the size of alkyl chains, and the best device performance can only be achieved with an optimized odd‐numbered alkyl chain. However, the synthetic route of odd‐numbered alkyl chains is costly and complicated, which makes it difficult for large‐scale synthesis. Here, this study presents a facile method to optimize the aggregation properties and blend morphology by employing donor polymers with a mixture of two even‐numbered, randomly distributed alkyl chains. In a model polymer system, this study suggests that the structural and electronic properties of the random polymers comprising a mixture of 2‐octyldodecyl and 2‐decyltetradecyl alkyl chains can be systematically tuned by varying the mixing ratio, and a high power conversion efficiency (11.1%) can be achieved. This approach promotes the scalability of donor polymers and thus facilitates the commercialization of PSCs.
DA - 2018/2/26/
PY - 2018/2/26/
DO - 10.1002/aenm.201701895
VL - 8
IS - 6
SP -
SN - 1614-6840
KW - fullerene
KW - high efficiency
KW - polymer solar cells
KW - random polymers
KW - side-chain engineering
ER -