@article{shanahan_yan_olanrewaju_kashani_ade_so_you_2024, title={Acid-Triggered Side Chain Cleavage Leads to Doped Conjugated Polymers of High Conductivity}, volume={10}, ISSN={["1520-5126"]}, DOI={10.1021/jacs.4c09843}, abstractNote={Cleavable side chain based conjugated polymers (CSCPs) represent a unique approach to offering solution processability with added benefits via the elimination of insulating side chains. This work highlights an optimally designed polythiophene-carboxylic acid based CSCP, POET-T2-COOH, which achieves a conductivity exceeding 350 S/cm in molecularly doped and side chain cleaved films, 100–100,000 times higher than three other structurally isomeric CSCPs. The high conductivity of POET-T2-COOH is accomplished via a new "cleavage with doping" methodology, synergistically combining a strong acid and a primary dopant. This hybrid method achieves the greatest conductivity in all isomeric CSCPs over conventional doping or cleavage techniques. The doped and side chain cleaved POET-T2-COOH displays a stable conductivity in inert atmospheres and a high work function of 5.3 eV, opening up new applications.}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Shanahan, Jordan and Yan, Liang and Olanrewaju, Yusuf and Kashani, Somayeh and Ade, Harald and So, Franky and You, Wei}, year={2024}, month={Oct} }
 @article{schrickx_kashani_buck_ding_rech_flagg_li_kudenov_you_richter_et al._2024, title={Exceptional Alignment in a Donor-Acceptor Conjugated Polymer via a Previously Unobserved Liquid Crystal Mesophase}, volume={4}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202315183}, abstractNote={AbstractOrienting polymer semiconductors is desirable to optimize device characteristics, provide insight into microstructure, and magnify subtle phase behavior. Here, a combination of uniaxial strain and subsequent heating of the donor–acceptor (DA) polymer PBnDT‐FTAZ is discovered to lead to exceptional optical dichroic ratios of up to 38 (and close to 50 near the polymer's absorption edge). This alignment is achieved due to the existence of a previously undetected thermotropic liquid crystal (LC) mesophase. The LC transition, not discernable through calorimetry, is uncovered through a combination of in situ UV–vis spectroscopy, X‐ray scattering, and dynamic mechanical analysis (DMA). Comparing PBnDT‐FTAZ to the non‐fluorinated PBnDT‐HTAZ and the homo polymer PBnDT, all of which show similar thermal transitions, reveals that exceptional alignment is only found in PBnDT‐FTAZ. This is attributed to the PBnDT‐FTAZ film having two distinct liquid crystal populations, and the polymer templating to a highly aligned, high‐clearing temperature population when heated. The DMA thermal relaxation behavior observed here is also seen in other DA conjugated polymers suggesting that such thermotropic LC mesophases may be common in these materials. These findings demonstrate a polymer semiconductor with remarkable alignment and uncover phase behavior with broad implications for process‐structure‐property relationships in polymer semiconductors.}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Schrickx, Harry M. and Kashani, Somayeh and Buck, Lauren and Ding, Kan and Rech, Jeromy J. and Flagg, Lucas Q. and Li, Ruipeng and Kudenov, Michael W. and You, Wei and Richter, Lee J. and et al.}, year={2024}, month={Apr} }
 @article{kwon_giridharagopal_neu_kashani_chen_quezada_guo_ade_you_ginger_2024, title={Quantifying Doping Efficiency to Probe the Effects of Nanoscale Morphology and Solvent Swelling in Molecular Doping of Conjugated Polymers}, volume={2}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.4c00153}, abstractNote={We study the doping of conjugated polymers from droplets of molecular dopant solutions, as might be used in additive manufacturing approaches. We compare the doping efficiency of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) solutions between two model conjugated polymers, regioregular poly(3-hexylthiophene) (P3HT) and poly(bithiophene-thienothiophene) copolymer with a triethylene glycol side chain (P(g32T-TT)). We find that F4TCNQ dopes P(g32T-TT) more efficiently from solution, producing films with >103 times higher conductivity. Using spectroelectrochemistry to calibrate polaron spectra to known hole injection levels, we quantify the doping efficiency (polarons created/dopant molecule added) to be higher than 170% for P(g32T-TT) but only 47.2% for P3HT. We further explore the differences in molecular doping using a combination of scanning Kelvin probe microscopy (SKPM) and conductive atomic force microscopy (cAFM). We explore doping efficiency and aggregation as a function of the solvent of the dopant solution, side chain, and regioregularity of conjugated polymers; we show that the doping efficiency and dopant aggregation are both correlated with the ability of the dopant/solvent solution to swell the conjugated polymer, with combinations that swell, resulting in more efficient doping and smoother films with less aggregation.}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Kwon, Sung-Joo and Giridharagopal, Rajiv and Neu, Justin and Kashani, Somayeh and Chen, Shinya E. and Quezada, Ramsess J. and Guo, Jiajie and Ade, Harald and You, Wei and Ginger, David S.}, year={2024}, month={Feb} }
 @article{ghaffari_kashani_do_weninger_riehn_2023, title={A nanophotonic interferometer}, volume={34}, ISSN={["1361-6528"]}, url={https://doi.org/10.1088/1361-6528/acb443}, DOI={10.1088/1361-6528/acb443}, abstractNote={Abstract
               The transmission of light through sub-wavelength apertures (zero-mode waveguides, ZMW) in metal films is well-explored. It introduces both an amplitude modulation as well as a phase shift to the oscillating electromagnetic field. We propose a nanophotonic interferometer by bringing two ZMW (∼100 nm diameter) in proximity and monitoring the distribution of transmitted light in the back-focal plane of collecting microscope objective (1.3 N.A.). We demonstrate that both an asymmetry induced by the binding of a quantum dot in one of the two ZMW, as well as an asymmetry in ZMW diameter yield qualitatively similar transmission patterns. We find that the complex pattern can be quantified through a scalar measure of asymmetry along the symmetry axis of the aperture pair. In a combined experimental and computational exploration of detectors with differing ZMW diameters, we find that the scalar asymmetry is a monotonous function of the diameter difference of the two apertures, and that the scalar asymmetry measure is higher if the sample is slightly displaced from the focal plane of the collecting microscope objective. An optimization of the detector geometry determined that the maximum response is achieved at an aperture separation that is comparable to the wavelength on the exit side of the sensor. For small separations of apertures, on the order of a quarter of the wavelength and less, the signal is strongly polarization dependent, while for larger separations, on the order of the wavelength or larger, the signal becomes essentially polarization-independent.}, number={18}, journal={NANOTECHNOLOGY}, author={Ghaffari, Abbas and Kashani, Somayeh and Do, Kevin and Weninger, Keith and Riehn, Robert}, year={2023}, month={Apr} }
 @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{kashani_wang_risko_ade_2022, title={Relating reorganization energies, exciton diffusion length and non-radiative recombination to the room temperature UV-vis absorption spectra of NF-SMA}, volume={12}, ISSN={["2051-6355"]}, url={https://doi.org/10.1039/D2MH01228F}, DOI={10.1039/d2mh01228f}, abstractNote={Multiparameter Franck–Condon analyses of absorption spectra of Y6 in dilute solutions reveals that Y6 exhibits a high conformation uniformity and the smallest intra-molecular reorganization energy among the materials studied.}, journal={MATERIALS HORIZONS}, author={Kashani, Somayeh and Wang, Zhen and Risko, Chad and Ade, Harald}, year={2022}, month={Dec} }
 @article{ghaffari_do_kashani_weninger_riehn_2022, title={A Nanophotonic Interferometer for small particle detection}, volume={12223}, ISBN={["978-1-5106-5430-3"]}, ISSN={["1996-756X"]}, DOI={10.1117/12.2634318}, abstractNote={The transmission of light through sub-wavelength apertures (zero-mode waveguides, ZMW) in metal films is wellexplored. It introduces both an amplitude modulation as well as a phase shift to the transmitted oscillating electromagnetic field. We propose a nanophotonic interferometer by bringing two zero-mode waveguides in proximity and monitoring the distribution of light in the back-focal plane of the collecting microscope objective. We demonstrate that both an asymmetry induced by the binding of a quantum dot in one of the two ZMW, as well as a asymmetry in ZMW diameter yield qualitatively similar deflection patterns. Using ZMW pairs with diameter asymmetries, we find that the complex pattern of the transmitted light can be quantified through a scalar measure of asymmetry along the symmetry axis of the aperture pair. We find that this scalar asymmetry is a monotonous function of the diameter difference of the two apertures.}, journal={INTERFEROMETRY XXI}, author={Ghaffari, A. and Do, K. and Kashani, S. and Weninger, K. and Riehn, Robert}, year={2022} }
 @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{balar_siddika_kashani_peng_rech_ye_you_ade_brendan t. o'conner_2020, title={Role of Secondary Thermal Relaxations in Conjugated Polymer Film Toughness}, volume={32}, ISSN={["1520-5002"]}, url={https://publons.com/wos-op/publon/35208553/}, DOI={10.1021/acs.chemmater.0c01910}, abstractNote={Conjugated polymers have proven to be an important class of materials for flexible and stretchable electronics. To ensure long term thermal and mechanical stability of associated devices, there is ...}, number={15}, journal={CHEMISTRY OF MATERIALS}, author={Balar, Nrup and Siddika, Salma and Kashani, Somayeh and Peng, Zhengxing and Rech, Jeromy James and Ye, Long and You, Wei and Ade, Harald and Brendan T. O'Conner}, year={2020}, month={Aug}, pages={6540–6549} }
 @article{king_melville_rice_kashani_tonnele_raboui_swaraj_grant_mcafee_bender_et al._2021, title={Silicon Phthalocyanines for n-Type Organic Thin-Film Transistors: Development of Structure-Property Relationships}, volume={3}, ISSN={["2637-6113"]}, DOI={10.1021/acsaelm.0c00871}, abstractNote={Silicon phthalocyanines (SiPcs) have shown great potential as n-type or ambipolar organic semiconductors in organic thin-film transistors (OTFTs) and organic photovoltaics. Although properly design...}, number={1}, journal={ACS APPLIED ELECTRONIC MATERIALS}, author={King, Benjamin and Melville, Owen A. and Rice, Nicole A. and Kashani, Somayeh and Tonnele, Claire and Raboui, Hasan and Swaraj, Sufal and Grant, Trevor M. and McAfee, Terry and Bender, Timothy P. and et al.}, year={2021}, month={Jan}, pages={325–336} }