@article{kashani_rech_liu_baustert_ghaffari_angunawela_xiong_dinku_you_graham_et al._2023, title={Exciton Binding Energy in Organic Polymers: Experimental Considerations and Tuning Prospects}, volume={12}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202302837}, abstractNote={AbstractDiscrepancies in reported values of exciton binding energy (Eb) for organic semiconductors (OSs) necessitate a comprehensive study. Traditionally, Eb is defined as the difference between the transport gap (Et) and the optical gap (Eopt). Here, the Eb values of PBnDT‐TAZ polymer variants are determined using two commonly employed methods: a combination of ultraviolet photoemission spectroscopy and low‐energy inverse photoemission spectroscopy (UPS‐LEIPS) and solid‐state cyclic voltammetry (CV). Eb values obtained by UPS‐LEIPS show low dispersion and no clear correlation with the polymer structure and thedielectric properties. In contrast, CV reveals a larger dispersion (200 meV‐1 eV) and an apparent qualitative Eb‐molecular structure correlation, as the lowest Eb values are observed for oligo‐ethylene glycol side chains. This discrepancy is discussed by examining the implications of the traditional definition of Eb. Additionally, the impact of both intrinsic and extrinsic factors contributing to the derived experimental values of Et is discussed. The differences in intrinsic and extrinsic factors highlight the context‐dependent nature of measurement when drawing global conclusions. Notably, the observed Eb trend derived from CV is not intrinsic to the pure materials but likely linked to electrolyte swelling and associated changes in dielectric environment, suggesting that high‐efficiency single‐material organic photovoltaics with low Eb may be possible via high dielectric materials.}, journal={ADVANCED ENERGY MATERIALS}, author={Kashani, Somayeh and Rech, Jeromy James and Liu, Tuo and Baustert, Kyle and Ghaffari, Abbas and Angunawela, Indunil and Xiong, Yuan and Dinku, Abay and You, Wei and Graham, Kenneth and et al.}, year={2023}, month={Dec} } @article{jia_ma_chen_meng_jain_angunawela_qin_kong_li_yang_et al._2023, title={Near-infrared absorbing acceptor with suppressed triplet exciton generation enabling high performance tandem organic solar cells}, volume={14}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-023-36917-y}, abstractNote={AbstractReducing the energy loss of sub-cells is critical for high performance tandem organic solar cells, while it is limited by the severe non-radiative voltage loss via the formation of non-emissive triplet excitons. Herein, we develop an ultra-narrow bandgap acceptor BTPSeV-4F through replacement of terminal thiophene by selenophene in the central fused ring of BTPSV-4F, for constructing efficient tandem organic solar cells. The selenophene substitution further decrease the optical bandgap of BTPSV-4F to 1.17 eV and suppress the formation of triplet exciton in the BTPSV-4F-based devices. The organic solar cells with BTPSeV-4F as acceptor demonstrate a higher power conversion efficiency of 14.2% with a record high short-circuit current density of 30.1 mA cm−2 and low energy loss of 0.55 eV benefitted from the low non-radiative energy loss due to the suppression of triplet exciton formation. We also develop a high-performance medium bandgap acceptor O1-Br for front cells. By integrating the PM6:O1-Br based front cells with the PTB7-Th:BTPSeV-4F based rear cells, the tandem organic solar cell demonstrates a power conversion efficiency of 19%. The results indicate that the suppression of triplet excitons formation in the near-infrared-absorbing acceptor by molecular design is an effective way to improve the photovoltaic performance of the tandem organic solar cells.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Jia, Zhenrong and Ma, Qing and Chen, Zeng and Meng, Lei and Jain, Nakul and Angunawela, Indunil and Qin, Shucheng and Kong, Xiaolei and Li, Xiaojun and Yang, Yang and et al.}, year={2023}, month={Mar} } @article{zhang_sun_angunawela_meng_qin_zhou_li_zhuo_yang_zhang_et al._2022, title={16.52% Efficiency All-Polymer Solar Cells with High Tolerance of the Photoactive Layer Thickness}, volume={4}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202108749}, abstractNote={AbstractAll‐polymer solar cells (all‐PSCs) have drawn growing attention and achieved tremendous progress recently, but their power conversion efficiency (PCE) still lags behind small‐molecule‐acceptor (SMA)‐based PSCs due to the relative difficulty on morphology control of polymer photoactive blends. Here, low‐cost PTQ10 is introduced as a second polymer donor (a third component) into the PM6:PY‐IT blend to finely tune the energy‐level matching and microscopic morphology of the polymer blend photoactive layer. The addition of PTQ10 decreases the π–π stacking distance, and increases the π–π stacking coherence length and the ordered face‐on molecular packing orientation, which improves the charge separation and transport in the photoactive layer. Moreover, the deeper highest occupied molecular orbital energy level of the PTQ10 polymer donor than PM6 leads to higher open‐circuit voltage of the ternary all‐PSCs. As a result, a PCE of 16.52% is achieved for ternary all‐PSCs, which is one of the highest PCEs for all‐PSCs. In addition, the ternary devices exhibit a high tolerance of the photoactive layer thickness with high PCEs of 15.27% and 13.91% at photoactive layer thickness of ≈205 and ≈306 nm, respectively, which are the highest PCEs so far for all‐PSCs with a thick photoactive layer.}, journal={ADVANCED MATERIALS}, author={Zhang, Wenqing and Sun, Chenkai and Angunawela, Indunil and Meng, Lei and Qin, Shucheng and Zhou, Liuyang and Li, Shaman and Zhuo, Hongmei and Yang, Guang and Zhang, Zhi-Guo and et al.}, year={2022}, month={Apr} } @article{yi_pan_chen_chen_angunawela_luo_zhang_zeng_chen_qi_et al._2022, title={A Benzo[1,2-b:4,5-b']Difuran Based Donor Polymer Achieving High-Performance (>17%) Single-Junction Organic Solar Cells with a Fill Factor of 80.4%}, volume={7}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202201850}, abstractNote={AbstractIn the field of non‐fullerene organic solar cells (OSCs), most of the promising polymer donors are based on benzo[1,2‐b:4,5‐b′]dithiophene (BDT) units while benzo[1,2‐b:4,5‐b′]difuran (BDF)‐based polymers have drawn less attention since the efficiencies of BDF polymer‐based devices are generally lower than those of BDT polymer‐based ones. In this contribution, the BDT unit in a polymer donor named D18 is replaced with a BDF unit, and a new polymer named D18‐Fu is synthesized. As a highly‐crystalline molecule named Y6‐1O is chosen as the acceptor, the efficiency of binary devices based on D18‐Fu can reach 16.38%. Furthermore, when one of fullerene derivatives PC71BM is added, the ternary devices based on D18‐Fu achieve an efficiency of 17.07% and a high fill factor (FF) of 80.4%, both of which are the highest values among those of BDF polymer‐based devices. For comparison, D18‐based ternary devices show an inferior efficiency of 15.61% mainly due to the lower FF of 73.9%. Subsequent characterization reveals that D18‐Fu possesses a more coplanar molecular geometry, leading to better morphology and higher charge mobility for a promising FF. The high performance shown in this work demonstrates the potential role of BDF units in the design of polymer donors for highly efficient OSCs.}, journal={ADVANCED ENERGY MATERIALS}, author={Yi, Jicheng and Pan, Mingao and Chen, Lu and Chen, Yuzhong and Angunawela, Indunil Chathurangani and Luo, Siwei and Zhang, Ting and Zeng, Anping and Chen, Jian and Qi, Zhenyu and et al.}, year={2022}, month={Jul} } @article{ho_pei_qin_zhang_peng_angunawela_jones_yin_iqbal_reynolds_et al._2022, title={Importance of Electric-Field-Independent Mobilities in Thick-Film Organic Solar Cells}, volume={10}, ISSN={["1944-8252"]}, url={http://dx.doi.org/10.1021/acsami.2c11265}, DOI={10.1021/acsami.2c11265}, abstractNote={In organic solar cells (OSCs), a thick active layer usually yields a higher photocurrent with broader optical absorption than a thin active layer. In fact, a ∼300 nm thick active layer is more compatible with large-area processing methods and theoretically should be a better spot for efficiency optimization. However, the bottleneck of developing high-efficiency thick-film OSCs is the loss in fill factor (FF). The origin of the FF loss is not clearly understood, and there a direct method to identify photoactive materials for high-efficiency thick-film OSCs is lacking. Here, we demonstrate that the mobility field-dependent coefficient is an important parameter directly determining the FF loss in thick-film OSCs. Simulation results based on the drift-diffusion model reveal that a mobility field-dependent coefficient smaller than 10-3 (V/cm)-1/2 is required to maintain a good FF in thick-film devices. To confirm our simulation results, we studied the performance of two ternary bulk heterojunction (BHJ) blends, PTQ10:N3:PC71BM and PM6:N3:PC71BM. We found that the PTQ10 blend film has weaker field-dependent mobilities, giving rise to a more balanced electron-hole transport at low fields. While both the PM6 blend and PTQ10 blend yield good performance in thin-film devices (∼100 nm), only the PTQ10 blend can retain a FF = 74% with an active layer thickness of up to 300 nm. Combining the benefits of a higher JSC in thick-film devices, we achieved a PCE of 16.8% in a 300 nm thick PTQ10:N3:PC71BM OSC. Such a high FF in the thick-film PTQ10 blend is also consistent with the observation of lower charge recombination from light-intensity-dependent measurements and lower energetic disorder observed in photothermal deflection spectroscopy.}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Ho, Carr Hoi Yi and Pei, Yusen and Qin, Yunpeng and Zhang, Chujun and Peng, Zhengxing and Angunawela, Indunil and Jones, Austin L. and Yin, Hang and Iqbal, Hamna F. and Reynolds, John R. and et al.}, year={2022}, month={Oct} } @article{luo_bai_zhang_zhao_angunawela_zou_li_luo_feng_yu_et al._2022, title={Optimizing spectral and morphological match of nonfullerene acceptors toward efficient indoor organic photovoltaics with enhanced light source adaptability}, volume={98}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2022.107281}, abstractNote={High-performance indoor organic photovoltaics (IOPV) require large-bandgap material systems to absorb visible light efficiently and reduce energy loss. However, state-of-the-art non-fullerene acceptors (NFAs) have absorptions in the near-infrared region and are thus not suitable for IOPV applications. Herein, we report a series of large-bandgap (>1.70 eV) NFAs named FCC-Cl-C8, FCC-Cl-4Ph and FCC-Cl-6Ph by modifying the alkyl side chains with alkylphenyl chains partially or completely. Results show that the bulky alkylphenyl side chains can finely tune the absorption properties of the NFAs and also affect their morphological properties. Interestingly, the best-performing NFA is the one (named FCC-Cl-4Ph) with partial alkyl and alkylphenyl substitutions, which blue-shift the absorption of the NFAs while minimizing the negative morphological effect of the bulky alkylphenyl chains. As a result, FCC-Cl-4Ph can achieve excellent indoor efficiencies over 29% under a 3000 K LED lamp at 1000 lux and show better solution processability over FCC-Cl-C8. More importantly, FCC-Cl-4Ph can maintain high indoor performance (29.7–26.8% at 1000 lux) under a wide range of indoor lighting spectra (2600, 3000, 4000, and 6500 K LED lamps), which should be due to the blue-shifted spectra of FCC-Cl-4Ph and better matching with various indoor conditions. This work reveals an interesting structure-property relationship and offers useful strategies for the further design of NFAs toward efficient IOPV devices.}, journal={NANO ENERGY}, author={Luo, Siwei and Bai, Fujin and Zhang, Jianquan and Zhao, Heng and Angunawela, Indunil and Zou, Xinhui and Li, Xiaojun and Luo, Zhenghui and Feng, Kui and Yu, Han and et al.}, year={2022}, month={Jul} } @article{li_kong_chen_angunawela_zhu_li_meng_ade_li_2022, title={Small-Molecule Acceptor with Unsymmetric Substituents and Fused Rings for High-Performance Organic Solar Cells with Enhanced Mobility and Reduced Energy Losses}, volume={11}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.2c17235}, abstractNote={A new unsymmetric small-molecule acceptor (SMA) BTPOSe-4F was designed by unsymmetric structure modification to Y6 with an alkyl upper side chain replaced by an alkoxy side chain and a sulfur atom in its central fused ring replaced by a selenium atom, for the application as an acceptor to fabricate organic solar cells (OSCs). BTPOSe-4F exhibits a higher lowest unoccupied molecular orbital (LUMO) energy level, a reduced nonradiation energy loss, and better charge extraction properties in its binary OSCs with a higher Voc of 0.886. Furthermore, the ternary OSCs with the addition of PC71BM demonstrated a higher power conversion efficiency (PCE) of 17.33% with Voc of 0.890 V. This work reveals that the unsymmetric modification strategy can further give impetus to the photovoltaic performance promotion of OSCs for Y6-series SMAs.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Li, Zechen and Kong, Xiaolei and Chen, Zeng and Angunawela, Indunil and Zhu, Haiming and Li, Xiaojun and Meng, Lei and Ade, Harald and Li, Yongfang}, year={2022}, month={Nov} } @article{steckmann_angunawela_kashani_zhu_nahid_ade_gadisa_2022, title={Ultrathin P(NDI2OD-T2) Films with High Electron Mobility in Both Bottom-Gate and Top-Gate Transistors}, volume={3}, ISSN={["2199-160X"]}, url={https://doi.org/10.1002/aelm.202101324}, DOI={10.1002/aelm.202101324}, abstractNote={AbstractUltrathin organic films (typically < 10 nm) attracted great attention due to their (semi)transparency and unique optoelectronic properties that benefit applications such as sensors and flexible electronics. At the core of that, achieving high mobility in an ultrathin film is essential for the efficient operation of relevant electronic devices. While the state‐of‐the‐art material systems, e.g., P(NDI2OD‐T2) also known as N2200 can achieve high mobility in a thin film (typically > 20 nm), multitudinous challenges remain in processing an ultrathin film exhibiting desired charge transport morphology within a preferred thickness limit. Here, high electron mobility (a tenfold increase compared to annealed spin‐coated films) is reported in both the top and bottom‐gate configuration organic field‐effect transistors comprising ultrathin N2200 films produced with a water‐floating film transfer method. A range of characterization techniques are used to investigate these ultrathin films and their microstructure, and conclude that favorable edge‐on polymer orientation at the top as well as throughout the ultrathin film thickness and the quality of π–π ordering as captured by the largest coherences length resulted in this high mobility in N2200 ultrathin films, in stark contrast to the commonly observed microstructural gradient in spin‐coated thin films. The results provide new insight into the electronic and microstructural properties of thin films of organic semiconductors.}, journal={ADVANCED ELECTRONIC MATERIALS}, author={Steckmann, Thomas and Angunawela, Indunil and Kashani, Somayeh and Zhu, Youqin and Nahid, Masrur M. and Ade, Harald and Gadisa, Abay}, year={2022}, month={Mar} } @article{zeng_ma_pan_chen_ma_zhao_zhang_kim_shang_luo_et al._2021, title={A Chlorinated Donor Polymer Achieving High-Performance Organic Solar Cells with a Wide Range of Polymer Molecular Weight}, volume={6}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202102413}, abstractNote={AbstractIn the field of non‐fullerene organic solar cells (OSCs), compared to the rapid development of non‐fullerene acceptors, the progress of high‐performance donor polymers is relatively slow. The property and performance of donor polymers in OSCs are often sensitive to the molecular weight of the polymers. In this study, a chlorinated donor polymer named D18‐Cl is reported, which can achieve high performance with a wide range of polymer molecular weight. The devices based on D18‐Cl show a higher open‐circuit voltage (VOC) due to the slightly deeper energy levels and an outstanding short‐circuit current density (JSC) owing to the appropriate long periods of blend films and less ([6,6]‐phenyl‐C71‐butyric acid methyl ester) (PC71BM) in mixed domains, leading to the higher efficiency of 17.97% than those of the D18‐based devices (17.21%). Meanwhile, D18‐Cl can achieve high efficiencies (17.30–17.97%) when its number‐averaged molecular weight (Mn) is ranged from 45 to 72 kDa. In contrast, the D18‐based devices only exhibit relatively high efficiencies in a narrow Mn range of ≈70 kDa. Such property and performance make D18‐Cl a promising donor polymer for scale‐up and low‐cost production.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Zeng, Anping and Ma, Xiaoling and Pan, Mingao and Chen, Yuzhong and Ma, Ruijie and Zhao, Heng and Zhang, Jianquan and Kim, Ha Kyung and Shang, Ao and Luo, Siwei and et al.}, year={2021}, month={Jun} } @article{yu_luo_sun_angunawela_qi_peng_zhou_han_wei_pan_et al._2021, title={A Difluoro-Monobromo End Group Enables High-Performance Polymer Acceptor and Efficient All-Polymer Solar Cells Processable with Green Solvent under Ambient Condition}, volume={31}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202100791}, abstractNote={AbstractIn this paper, a difluoro‐monobromo end group is designed and synthesized, which is then used to construct a novel polymer acceptor (named PY2F‐T) yielding high‐performance all‐polymer solar cells with 15.22% efficiency. The fluorination strategy can increase the intramolecular charge transfer and interchain packing of the previous PY‐T based acceptor, and significantly improve photon harvesting and charge mobility of the resulting polymer acceptor. In addition, detailed morphology investigations reveal that the PY2F‐T‐based blend shows smaller domain spacing and higher domain purity, which significantly suppress charge recombination as supported by time‐resolved techniques. These polymer properties enable simultaneously enhanced JSC and FF of the PY2F‐T‐based devices, eventually delivering device efficiencies of over 15%, significantly outperforming that of the devices based on the non‐fluorinated PY‐T polymer (13%). More importantly, the PY2F‐T‐based active layers can be processed under ambient conditions and still achieve a 14.37% efficiency. They can also be processed using non‐halogenated solvent o‐xylene (no additive) and yield a decent performance of 13.05%. This work demonstrates the success of the fluorination strategy in the design of high‐performance polymer acceptors, which provide guidelines for developing new all‐PSCs with better efficiencies and stabilities for commercial applications.}, number={25}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Yu, Han and Luo, Siwei and Sun, Rui and Angunawela, Indunil and Qi, Zhenyu and Peng, Zhengxing and Zhou, Wentao and Han, Han and Wei, Rong and Pan, Mingao and et al.}, year={2021}, month={Jun} } @article{zhang_bai_angunawela_xu_luo_li_chai_yu_chen_hu_et al._2021, title={Alkyl-Chain Branching of Non-Fullerene Acceptors Flanking Conjugated Side Groups toward Highly Efficient Organic Solar Cells}, volume={10}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202102596}, abstractNote={AbstractSide‐chain modifications of non‐fullerene acceptors (NFAs) are essential for harvesting their full potential in organic solar cells (OSC). Here, an effective alkyl‐chain‐branching approach of the Y‐series NFAs flanking meta‐substituted phenyl side groups at the outer positions is demonstrated. Compared to BTP‐4F‐PC6 with linear m‐hexylphenyl chains, two new acceptors named BTP‐4F‐P2EH and BTP‐4F‐P3EH are developed with bulkier alkyl chains branched at the β and γ positions, respectively. These branched chains result in altered molecular packing of the NFAs and afford higher open‐circuit voltage of the devices. Despite the blue‐shifted absorption of the branched‐chain NFAs, their blends with PBDB‐T‐2F enable improved short‐circuit current density for the corresponding devices owing to the more suitable phase separation and better exciton dissociation. Consequently, the OSCs based on BTP‐4F‐P2EH and BTP‐4F‐P3EH yield enhanced device performance of 18.22% and 17.57%, respectively, outperforming the BTP‐4F‐PC6‐based ones (17.22%). These results highlight that the side‐chain branching design of NFAs has great potential in optimizing molecular properties and promoting photovoltaic performance.}, journal={ADVANCED ENERGY MATERIALS}, author={Zhang, Jianquan and Bai, Fujin and Angunawela, Indunil and Xu, Xiaoyun and Luo, Siwei and Li, Chao and Chai, Gaoda and Yu, Han and Chen, Yuzhong and Hu, Huawei and et al.}, year={2021}, month={Oct} } @article{jia_qin_meng_ma_angunawela_zhang_li_he_lai_li_et al._2021, title={High performance tandem organic solar cells via a strongly infrared-absorbing narrow bandgap acceptor}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-020-20431-6}, abstractNote={AbstractTandem organic solar cells are based on the device structure monolithically connecting two solar cells to broaden overall absorption spectrum and utilize the photon energy more efficiently. Herein, we demonstrate a simple strategy of inserting a double bond between the central core and end groups of the small molecule acceptor Y6 to extend its conjugation length and absorption range. As a result, a new narrow bandgap acceptor BTPV-4F was synthesized with an optical bandgap of 1.21 eV. The single-junction devices based on BTPV-4F as acceptor achieved a power conversion efficiency of over 13.4% with a high short-circuit current density of 28.9 mA cm−2. With adopting BTPV-4F as the rear cell acceptor material, the resulting tandem devices reached a high power conversion efficiency of over 16.4% with good photostability. The results indicate that BTPV-4F is an efficient infrared-absorbing narrow bandgap acceptor and has great potential to be applied into tandem organic solar cells.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Jia, Zhenrong and Qin, Shucheng and Meng, Lei and Ma, Qing and Angunawela, Indunil and Zhang, Jinyuan and Li, Xiaojun and He, Yakun and Lai, Wenbin and Li, Ning and et al.}, year={2021}, month={Jan} } @article{zhou_meng_zhang_zhu_qin_angunawela_wan_ade_li_2021, title={Introducing Low-Cost Pyrazine Unit into Terpolymer Enables High-Performance Polymer Solar Cells with Efficiency of 18.23%}, volume={11}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202109271}, abstractNote={AbstractRecently, a random ternary copolymerization strategy has become a promising and efficient approach to develop high‐performance polymer donors for polymer solar cells (PSCs). In this study, a low‐cost electron‐withdrawing unit, 2,5‐bis(4‐(2‐ethylhexyl)thiophen‐2‐yl)pyrazine (PZ‐T), is incorporated into the polymer backbone of PM6 as the third component, and three D‐A1‐D‐A2 type terpolymers PMZ‐10, PMZ‐20, and PMZ‐30 are synthesized by the random copolymerization strategy, with the PZ‐T proportion of 10%, 20%, and 30%, respectively. The terpolymers exhibit downshifted highest occupied molecular orbital energy levels than PM6, which is beneficial for obtaining higher open‐circuit voltage (Voc) of the PSCs with the polymer as a donor. Importantly, the PSCs based on PMZ‐10:Y6 demonstrate efficient exciton dissociation, higher and balanced electron/hole mobilities, desirable aggregation, and high power conversion efficiency of 18.23%, which is the highest efficiency among the terpolymer‐based PSCs so far. The results indicate that the ternary copolymerization strategy with PZ‐T as the second A‐unit is an efficient approach to further improve the photovoltaic performance and reduce the synthetic cost of the D‐A copolymer donors.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Zhou, Liuyang and Meng, Lei and Zhang, Jinyuan and Zhu, Can and Qin, Shucheng and Angunawela, Indunil and Wan, Yan and Ade, Harald and Li, Yongfang}, year={2021}, month={Nov} } @article{du_hu_zhang_meng_yue_angunawela_yan_qin_kong_zhang_et al._2021, title={Polymerized small molecular acceptor based all-polymer solar cells with an efficiency of 16.16% via tuning polymer blend morphology by molecular design}, volume={12}, ISSN={["2041-1723"]}, DOI={10.1038/s41467-021-25638-9}, abstractNote={AbstractAll-polymer solar cells (all-PSCs) based on polymerized small molecular acceptors (PSMAs) have made significant progress recently. Here, we synthesize two A-DA’D-A small molecule acceptor based PSMAs of PS-Se with benzo[c][1,2,5]thiadiazole A’-core and PN-Se with benzotriazole A’-core, for the studies of the effect of molecular structure on the photovoltaic performance of the PSMAs. The two PSMAs possess broad absorption with PN-Se showing more red-shifted absorption than PS-Se and suitable electronic energy levels for the application as polymer acceptors in the all-PSCs with PBDB-T as polymer donor. Cryogenic transmission electron microscopy visualizes the aggregation behavior of the PBDB-T donor and the PSMA in their solutions. In addition, a bicontinuous-interpenetrating network in the PBDB-T:PN-Se blend film with aggregation size of 10~20 nm is clearly observed by the photoinduced force microscopy. The desirable morphology of the PBDB-T:PN-Se active layer leads its all-PSC showing higher power conversion efficiency of 16.16%.}, number={1}, journal={NATURE COMMUNICATIONS}, author={Du, Jiaqi and Hu, Ke and Zhang, Jinyuan and Meng, Lei and Yue, Jiling and Angunawela, Indunil and Yan, Hongping and Qin, Shucheng and Kong, Xiaolei and Zhang, Zhanjun and et al.}, year={2021}, month={Sep} } @article{bin_angunawela_ma_nallapaneni_zhu_leenaers_saes_wienk_yan_ade_et al._2020, title={Effect of main and side chain chlorination on the photovoltaic properties of benzodithiophene-alt-benzotriazole polymers}, volume={8}, ISSN={["2050-7534"]}, DOI={10.1039/d0tc03095c}, abstractNote={Introduction of chlorine in the conjugated side chains significantly improves open-circuit voltage and power conversion efficiency, benefiting from a lower HOMO energy level, well-balanced charge transport and superior nanoscale morphology.}, number={43}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Bin, Haijun and Angunawela, Indunil and Ma, Ruijie and Nallapaneni, Asritha and Zhu, Chenhui and Leenaers, Pieter J. and Saes, Bart W. H. and Wienk, Martijn M. and Yan, He and Ade, Harald and et al.}, year={2020}, month={Nov}, pages={15426–15435} } @article{li_angunawela_chang_zhou_huang_zhong_liebman-pelaez_zhu_meng_xie_et al._2020, title={Effect of the chlorine substitution position of the end-group on intermolecular interactions and photovoltaic performance of small molecule acceptors}, volume={13}, ISSN={["1754-5706"]}, DOI={10.1039/d0ee02251a}, abstractNote={Differences in the intermolecular interactions of small molecule acceptors with different chlorine substitution positions affect their molecular packing and photovoltaic properties.}, number={12}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Li, Xiaojun and Angunawela, Indunil and Chang, Yuan and Zhou, Jiadong and Huang, He and Zhong, Lian and Liebman-Pelaez, Alex and Zhu, Chenhui and Meng, Lei and Xie, Zengqi and et al.}, year={2020}, month={Dec}, pages={5028–5038} } @article{huang_li_sun_angunawela_qiu_du_qin_meng_zhang_ade_et al._2020, title={Green solvent-processed organic solar cells based on a low cost polymer donor and a small molecule acceptor}, volume={8}, ISSN={["2050-7534"]}, DOI={10.1039/d0tc01313g}, abstractNote={High-performance OSCs were fabricated based on polymer PTQ10 as donor and HO-IDIC-2F as acceptor, using non-halogen tetrahydrofuran as processing solvent and the PCE of the as-cast OSCs reached 12.20% which is competitive with regular chloroform.}, number={23}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Huang, He and Li, Xiaojun and Sun, Chenkai and Angunawela, Indunil and Qiu, Beibei and Du, Jiaqi and Qin, Shucheng and Meng, Lei and Zhang, Zhanjun and Ade, Harald and et al.}, year={2020}, month={Jun}, pages={7718–7724} } @article{du_hu_meng_angunawela_zhang_qin_liebman-pelaez_zhu_zhang_ade_et al._2020, title={High-Performance All-Polymer Solar Cells: Synthesis of Polymer Acceptor by a Random Ternary Copolymerization Strategy}, volume={59}, ISSN={["1521-3773"]}, DOI={10.1002/anie.202005357}, abstractNote={AbstractDemonstrated in this work is a simple random ternary copolymerization strategy to synthesize a series of polymer acceptors, PTPBT‐ETx, by polymerizing a small‐molecule acceptor unit modified from Y6 with a thiophene connecting unit and a controlled amount of an 3‐ethylesterthiophene (ET) unit. Compared to PTPBT of only Y6‐like units and thiophene units, PTPBT‐ETx (where x represents the molar ratio of the ET unit) with an incorporated ET unit in the ternary copolymers show up‐shifted LUMO energy levels, increased electron mobilities, and improved blend morphologies in the blend film with the polymer donor PBDB‐T. And the all‐polymer solar cell (all‐PSC) based on PBDB‐T:PTPBT‐ET0.3 achieved a high power conversion efficiency over 12.5 %. In addition, the PTPBT‐ET0.3‐based all‐PSC also exhibits long‐term photostability over 300 hours.}, number={35}, journal={ANGEWANDTE CHEMIE-INTERNATIONAL EDITION}, author={Du, Jiaqi and Hu, Ke and Meng, Lei and Angunawela, Indunil and Zhang, Jinyuan and Qin, Shucheng and Liebman-Pelaez, Alex and Zhu, Chenhui and Zhang, Zhanjun and Ade, Harald and et al.}, year={2020}, month={Aug}, pages={15181–15185} } @article{bin_angunawela_qiu_colberts_li_dyson_wienk_ade_li_janssen_2020, title={Precise Control of Phase Separation Enables 12% Efficiency in All Small Molecule Solar Cells}, volume={10}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202001589}, DOI={10.1002/aenm.202001589}, abstractNote={AbstractCompared to conjugated polymers, small‐molecule organic semiconductors present negligible batch‐to‐batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small‐molecular organic solar cells (SM‐OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small‐molecular donors H13 and H14, created by fluorine and chlorine substitution of the original donor molecule H11, are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open‐circuit voltage with IDIC‐4F as acceptor. Due to kinetic and thermodynamic reasons, H13‐based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14‐based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14‐based SM‐OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM‐OSCs using IDIC‐4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine‐tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.}, number={34}, journal={ADVANCED ENERGY MATERIALS}, publisher={Wiley}, author={Bin, Haijun and Angunawela, Indunil and Qiu, Beibei and Colberts, Fallon J. M. and Li, Mengmeng and Dyson, Matthew J. and Wienk, Martijn M. and Ade, Harald and Li, Yongfang and Janssen, Rene A. J.}, year={2020}, month={Sep} } @article{liu_kumagai_manzhos_chen_angunawela_nahid_feron_bottle_bell_ade_et al._2020, title={Synergistic Use of Pyridine and Selenophene in a Diketopyrrolopyrrole-Based Conjugated Polymer Enhances the Electron Mobility in Organic Transistors}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202000489}, abstractNote={AbstractTo achieve semiconducting materials with high electron mobility in organic field‐effect transistors (OFETs), low‐lying energy levels (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) and favorable molecular packing and ordering are two crucial factors. Here, it is reported that the incorporation of pyridine and selenophene into the backbone of a diketopyrrolopyrrole (DPP)‐based copolymer produces a high‐electron‐mobility semiconductor, PDPPy‐Se. Compared with analogous polymers based on other DPP derivatives and selenophene, PDPPy‐Se features a lower LUMO that can decrease the electron transfer barrier for more effective electron injection, and simultaneously a lower HOMO that, however, can increase the hole transfer barrier to suppress the hole injection. Combined with thermal annealing at 240 °C for thin film morphology optimization to achieve large‐scale crystallite domains with tight molecular packing for effective charge transport along the conducting channel, OFET devices fabricated with PDPPy‐Se exhibit an n‐type‐dominant performance with an electron mobility (μe) as high as 2.22 cm2 V−1 s−1 and a hole/electron mobility ratio (μh/μe) of 0.26. Overall, this study demonstrates a simple yet effective approach to boost the electron mobility in organic transistors by synergistic use of pyridine and selenophene in the backbone of a DPP‐based copolymer.}, number={34}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Liu, Qian and Kumagai, Shohei and Manzhos, Sergei and Chen, Yingqian and Angunawela, Indunil and Nahid, Masrur Morshed and Feron, Krishna and Bottle, Steven E. and Bell, John and Ade, Harald and et al.}, year={2020}, month={Aug} } @article{ghasemi_hu_peng_rech_angunawela_carpenter_stuard_wadsworth_mcculloch_you_et al._2019, title={Delineation of Thermodynamic and Kinetic Factors that Control Stability in Non-fullerene Organic Solar Cells}, volume={3}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2019.03.020}, abstractNote={Although non-fullerene small molecular acceptors (NF-SMAs) are dominating current research in organic solar cells (OSCs), measurements of thermodynamics drivers and kinetic factors determining their morphological stability are lacking. Here, we delineate and measure such factors in crystallizable NF-SMA blends and discuss four model systems with respect to their meta-stability and degree of vitrification. We determine for the first time the amorphous-amorphous phase diagram in an NF-SMA system and show that its deep quench depth can result in severe burn-in degradation. We estimate the relative phase behavior of four other materials systems. Additionally, we derive room-temperature diffusion coefficients and conclude that the morphology needs to be stabilized by vitrification corresponding to diffusion constants below 10−22 cm2/s. Our results show that to achieve stability via rational molecular design, the thermodynamics, glass transition temperature, diffusion properties, and related structure-function relations need to be more extensively studied and understood.}, number={5}, journal={JOULE}, author={Ghasemi, Masoud and Hu, Huawei and Peng, Zhengxing and Rech, Jeromy James and Angunawela, Indunil and Carpenter, Joshua H. and Stuard, Samuel J. and Wadsworth, Andrew and McCulloch, Iain and You, Wei and et al.}, year={2019}, month={May}, pages={1328–1348} } @article{zhong_bin_angunawela_jia_qiu_sun_li_zhang_ade_li_2019, title={Effect of Replacing Thiophene by Selenophene on the Photovoltaic Performance of Wide Bandgap Copolymer Donors}, volume={52}, ISSN={["1520-5835"]}, DOI={10.1021/acs.macromol.9b00484}, abstractNote={Two polymers J75 and J76 with selenophene instead of thiophene on the conjugated side chain of benzodithiophene (BDT) unit or π bridges of polymer J71 were designed and synthesized, for investigating the effect of selenophene substitution on the photovoltaic performance of the conjugated polymer donors in comparison with J71. The selenophene π bridges in J76 can narrow optical band gap and red-shift absorption of the polymer film by ca. 25 nm, but the highest occupied molecular orbital (HOMO) energy level (EHOMO) of J76 is up-shifted slightly by 0.04 eV. Two typical electron acceptors of fullerene derivative PC71BM and the nonfullerene acceptor m-ITIC were used to investigate photovoltaic performance of the polymer donors. For the PC71BM-based polymer solar cells (PSCs), J76 with selenophene π bridges shows the best power-conversion efficiency (PCE) of 8.40% in comparison with the J71-based device (PCE = 6.79%), benefitted from the red-shifted absorption, larger coherence length, purer average domains, an...}, number={12}, journal={MACROMOLECULES}, author={Zhong, Lian and Bin, Haijun and Angunawela, Indunil and Jia, Zhenrong and Qiu, Beibei and Sun, Chenkai and Li, Xiaojun and Zhang, Zhanjun and Ade, Harald and Li, Yongfang}, year={2019}, month={Jun}, pages={4776–4784} } @article{li_huang_angunawela_zhou_du_liebman-pelaez_zhu_zhang_meng_xie_et al._2020, title={Effects of Short-Axis Alkoxy Substituents on Molecular Self-Assembly and Photovoltaic Performance of Indacenodithiophene-Based Acceptors}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201906855}, abstractNote={AbstractThe effects of central alkoxy side chain length of a series of narrow bandgap small molecule acceptors (SMAs) on their physicochemical properties and on the photovoltaic performance of the SMA‐based polymer solar cells (PSCs) are systematically investigated. It is found that the ordered aggregation of these SMAs in films is enhanced gradually with the increase of alkoxy chain length. The single‐crystal structures of these SMAs further reveal that small changes in the side chain length can have a dramatic impact on molecular self‐assembly. The short‐circuit current density and power conversion efficiency values of the corresponding PSCs increase with the increase of the side chain length of the SMAs. The π–π coherence length of the SMAs in the active layers is increased with the increase of the side chain length, which could be the reason for the increase of the Jsc in the PSCs. The results indicate that small changes in side chain length can have a dramatic impact on the molecular self‐assembly, morphology, and photovoltaic performance of the PSCs. The structure–performance relationship established in this study can provide important instructions for the side chain engineering and for the design of efficient SMAs materials.}, number={3}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Li, Xiaojun and Huang, He and Angunawela, Indunil and Zhou, Jiadong and Du, Jiaqi and Liebman-Pelaez, Alex and Zhu, Chenhui and Zhang, Zhanjun and Meng, Lei and Xie, Zengqi and et al.}, year={2020}, month={Jan} } @article{ma_xue_zhong_angunawela_chen_ade_huo_zhang_li_2019, title={High voltage all polymer solar cells with a polymer acceptor based on NDI and benzotriazole}, volume={7}, ISSN={["2050-7534"]}, DOI={10.1039/c9tc01922g}, abstractNote={A new n-type conjugated copolymer LA03 based on naphthalene diimide and benzotriazole with thiophene π-bridges was synthesized, and the all polymer solar cells with PBDB-T as donor and LA03 as acceptor achieved a power conversion efficiency of 6.49%.}, number={29}, journal={JOURNAL OF MATERIALS CHEMISTRY C}, author={Ma, Qing and Xue, Xiaonan and Zhong, Lian and Angunawela, Indunil and Chen, Shanshan and Ade, Harald and Huo, Lijun and Zhang, Zhanjun and Li, Yongfang}, year={2019}, month={Aug}, pages={9031–9037} } @article{pan_sun_bin_angunawela_lai_meng_ade_li_2020, title={Side-chain engineering of medium bandgap polymer donors for efficient polymer solar cells}, volume={78}, ISSN={["1878-5530"]}, DOI={10.1016/j.orgel.2019.105603}, abstractNote={Polymer solar cells (PSCs) have received widespread attentions recently due to the significant innovations of narrow bandgap n-type organic semiconductor (n-OS) acceptors. To obtain efficient PSCs, it is crucial to employ suitable donor/acceptor pair with matched electronic energy levels, complementary absorption spectra, appropriate molecular self-assembly behavior and preferred blend film morphology, which can be achieved by rational molecular structure optimization. Here we develop three D-A copolymer donors J55, J65 and J75 based on identical building blocks of bithienyl-benzodithiophene (BDTT) D-unit and bifluorine substituted benzotriazole A-unit with different flexible side-chains on BDTT unit to regulate the molecular electronic energy levels and molecular aggregation features, for further improving photovoltaic performance of the PSCs. The three D-A copolymers showed similar absorption profiles due to the identical building blocks. In comparison with the alkyl side-chain substituted polymer J55, the polymers J65 and J75 with alkylthio side-chain and alkylsilyl side-chain showed gradually down-shifted highest occupied molecular orbital energy levels (EHOMO) of −5.38 and −5.43 eV, respectively, which is beneficial for obtaining high open-circuit voltage (Voc). The favorable morphology with preferred face-on orientation and stronger integrated intensity of the π-π stacking peak was formed in J75 blend, which contributes to charge transport, thus enhancing the fill factor (FF) and Jsc. The PSC with J75 as donor and ITIC as acceptor exhibits an efficient PCE of 11.07%, with a Voc of 0.94 V, an enhanced Jsc of 16.99 mA cm−2 and a high FF of 69.29%.}, journal={ORGANIC ELECTRONICS}, author={Pan, Fei and Sun, Chenkai and Bin, Haijun and Angunawela, Indunil and Lai, Wenbin and Meng, Lei and Ade, Harald and Li, Yongfang}, year={2020}, month={Mar} } @article{carpenter_ghasemi_gann_angunawela_stuard_rech_ritchie_brendan t. o'connor_atkin_you_et al._2019, title={Competition between Exceptionally Long-Range Alkyl Sidechain Ordering and Backbone Ordering in Semiconducting Polymers and Its Impact on Electronic and Optoelectronic Properties}, volume={29}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201806977}, abstractNote={AbstractIntra‐ and intermolecular ordering greatly impacts the electronic and optoelectronic properties of semiconducting polymers. The interrelationship between ordering of alkyl sidechains and conjugated backbones has yet to be fully detailed, despite much prior effort. Here, the discovery of a highly ordered alkyl sidechain phase in six representative semiconducting polymers, determined from distinct spectroscopic and diffraction signatures, is reported. The sidechain ordering exhibits unusually large coherence lengths (≥70 nm), induces torsional/twisting backbone disorder, and results in a vertically multilayered nanostructure with ordered sidechain layers alternating with disordered backbone layers. Calorimetry and in situ variable temperature scattering measurements in a model system poly{4‐(5‐(4,8‐bis(3‐butylnonyl)‐6‐methylbenzo[1,2‐b:4,5‐b′]dithiophen‐2‐yl)thiophen‐2‐yl)‐2‐(2‐butyloctyl)‐5,6‐difluoro‐7‐(5‐methylthiophen‐2‐yl)‐2H‐benzo[d][1,2,3]triazole} (PBnDT‐FTAZ) clearly delineate this competition of ordering that prevents simultaneous long‐range order of both moieties. The long‐range sidechain ordering can be exploited as a transient state to fabricate PBnDT‐FTAZ films with an atypical edge‐on texture and 2.5× improved field‐effect transistor mobility. The observed influence of ordering between the moieties implies that improved molecular design can produce synergistic rather than destructive ordering effects. Given the large sidechain coherence lengths observed, such synergistic ordering should greatly improve the coherence length of backbone ordering and thereby improve electronic and optoelectronic properties such as charge transport and exciton diffusion lengths.}, number={5}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Carpenter, Joshua H. and Ghasemi, Masoud and Gann, Eliot and Angunawela, Indunil and Stuard, Samuel J. and Rech, Jeromy James and Ritchie, Earl and Brendan T. O'Connor and Atkin, Joanna and You, Wei and et al.}, year={2019}, month={Feb} } @article{bin_yao_yang_angunawela_sun_gao_ye_qiu_xue_zhu_et al._2018, title={High-Efficiency All-Small-Molecule Organic Solar Cells Based on an Organic Molecule Donor with Alkylsilyl-Thienyl Conjugated Side Chains}, volume={30}, ISSN={["1521-4095"]}, url={https://publons.com/wos-op/publon/7528268/}, DOI={10.1002/adma.201706361}, abstractNote={AbstractTwo 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.}, number={27}, journal={ADVANCED MATERIALS}, author={Bin, Haijun and Yao, Jia and Yang, Yankang and Angunawela, Indunil and Sun, Chenkai and Gao, Liang and Ye, Long and Qiu, Beibei and Xue, Lingwei and Zhu, Chenhui and et al.}, year={2018}, month={Jul} } @article{li_yao_angunawela_sun_xue_liebman-pelaez_zhu_yang_zhang_ade_et al._2018, title={Improvement of Photovoltaic Performance of Polymer Solar Cells by Rational Molecular Optimization of Organic Molecule Acceptors}, volume={8}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.201800815}, abstractNote={AbstractTwo 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.}, number={23}, journal={ADVANCED ENERGY MATERIALS}, author={Li, Xiaojun and Yao, Jia and Angunawela, Indunil and Sun, Chenkai and Xue, Lingwei and Liebman-Pelaez, Alexander and Zhu, Chenhui and Yang, Chunhe and Zhang, Zhi-Guo and Ade, Harald and et al.}, year={2018}, month={Aug} } @article{angunawela_ye_bin_zhang_gadisa_li_ade_2019, title={Multi-length scale morphology of nonfullerene all-small molecule blends and its relation to device function in organic solar cells}, volume={3}, ISSN={["2052-1537"]}, url={https://doi.org/10.1039/C8QM00503F}, DOI={10.1039/c8qm00503f}, abstractNote={Device characteristics of a pair of nonfullerene small molecule solar cells were well correlated to their mesoscale morphologyviaresonant soft X-ray scattering.}, number={1}, journal={MATERIALS CHEMISTRY FRONTIERS}, publisher={Royal Society of Chemistry (RSC)}, author={Angunawela, Indunil and Ye, Long and Bin, Haijun and Zhang, Zhi-Guo and Gadisa, Abay and Li, Yongfang and Ade, Harald}, year={2019}, month={Jan}, pages={137–144} }