@article{wang_peng_balar_ade_2023, title={Suppressing pre-aggregation to increase polymer solar cell ink shelf life}, volume={11}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta06617g}, abstractNote={Chemical degradation and morphology failure of ink-processed organic solar cells are now extensively studied. In contrast, the general problem that inks prepared via thermal and mechanical agitation degrade and age...}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Wang, Zhen and Peng, Zhengxing and Balar, Nrup and Ade, Harald}, year={2023}, month={Nov} }
 @article{ng_kwok_qi_wang_chen_liu_zhao_ade_zhang_yan_et al._2023, title={Synergistic effect of benzoselenadiazole core and alkoxy side chain substitution on the photovoltaic performance of non-fullerene acceptors}, volume={10}, ISSN={["2050-7496"]}, DOI={10.1039/d3ta04364a}, abstractNote={“Y-series” small-molecule acceptors (SMAs) have attracted extensive research interest as they boost the power conversion efficiencies of organic solar cells (OSCs). Since then, research communities began to concentrate on the...}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Ng, Ho Ming and Kwok, Chung Hang and Qi, Zhenyu and Wang, Zhen and Chen, Li and Liu, Wei and Zhao, Wenchao and Ade, Harald and Zhang, Chen and Yan, He and et al.}, year={2023}, month={Oct} }
 @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={Understanding excited-state reorganization energies, exciton diffusion lengths and non-radiative (NR) recombination, and the overall optoelectronic responses of nonfullerene small molecule acceptors (NF-SMAs) is important in order to rationally design new materials with controlled properties. While the effects of structural modifications on the optical gaps and electron affinities of NF-SMAs have been studied extensively, analyses of their absorption spectra that carefully characterize electronic and vibrational contributions that allow comparisons of reorganization energies and their implications for exciton diffusion lengths and NR recombination have yet to be reported. Here, we study the room temperature absorption spectra of three structural classes of NF-SMAs in dilute solutions through multiparameter Franck Condon (MFC) analyses and density functional theory (DFT) calculations. We show that the absorption spectra of these NF-SMAs can be categorized based on molecular structure-spectra correlation. The absorption spectra of curved, Y6-like structures can be described using an MFC model with two electronic transitions and two effective vibrational modes. The results of MFC/DFT analyses reveal that Y6 exhibits the smallest intra-molecular reorganization energy among the materials studied. Linear ITIC-like molecular structures reveal larger reorganization energies and reduced conformational uniformity compared to Y6. Meanwhile structures such as IDTBR and IEICO, which have an extra π-conjugated moiety between the donor and acceptor moieties, have large excited-state reorganization energies and low degrees of conformational uniformity. Since the intra-molecular reorganization energy is correlated with exciton diffusion length and nonradiative voltage losses (ΔVnr), our results highlight the power of RT absorption spectroscopy and DFT calculations as simple tools to designing improved OSCs materials with small reorganization energies, small ΔVnr, large exciton diffusion length and low energetic disorder (due to a strongly dominant conformation).}, journal={MATERIALS HORIZONS}, author={Kashani, Somayeh and Wang, Zhen and Risko, Chad and Ade, Harald}, year={2022}, month={Dec} }
 @article{fang_wang_chen_zhang_zhang_zhu_zhang_cui_wei_ade_et al._2022, title={Revealing aggregation of non-fullerene acceptors in intermixed phase by ultraviolet-visible absorption spectroscopy}, volume={3}, ISSN={["2666-3864"]}, DOI={10.1016/j.xcrp.2022.100983}, abstractNote={Non-fullerene acceptor (NFA) aggregation is crucial in determining bulk-heterojunction (BHJ) organic photovoltaic (OPV) performance. However, it is still a big challenge to characterize the nanostructure of NFAs in the disordered donor-acceptor intermixed phase. Here, we demonstrate a method to characterize NFA aggregation and composition in the intermixed phase by measuring NFA concentration-dependent ultraviolet-visible (UV-vis) absorption spectroscopy of BHJ films. In various polymer:NFA films, an absorption shift as a function of increasing molecular concentration (ASIMC) phenomenon is observed, and different NFA aggregation behaviors can be distinguished. The ASIMC method was then applied to study the influence of processing conditions on the NFA concentration in the intermixed phase of devices to establish a correlation with device efficiency. The current work provides a feasible tool to study the nanostructure of NFAs in the complex polymer matrix and to understand the variations in the NFA concentration in the intermixed phase under non-equilibrium conditions.}, number={7}, journal={CELL REPORTS PHYSICAL SCIENCE}, author={Fang, Jin and Wang, Zhen and Chen, Yiyao and Zhang, Qing and Zhang, Jianqi and Zhu, Lingyun and Zhang, Maojie and Cui, Zheng and Wei, Zhixiang and Ade, Harald and et al.}, year={2022}, month={Jul} }
 @article{rech_yan_wang_zhang_bradshaw_ade_you_2021, title={Functionalization of Benzotriazole-Based Conjugated Polymers for Solar Cells: Heteroatom vs Substituents}, volume={3}, ISSN={["2637-6105"]}, DOI={10.1021/acsapm.0c00761}, abstractNote={With the recent remarkable advances in the efficiency of organic solar cells, the need to distill key structure–property relationships for semiconducting materials cannot be understated. The fundam...}, number={1}, journal={ACS APPLIED POLYMER MATERIALS}, author={Rech, Jeromy James and Yan, Liang and Wang, Zhen and Zhang, Qianqian Q. and Bradshaw, Spencer and Ade, Harald and You, Wei}, year={2021}, month={Jan}, pages={30–41} }
 @article{zhang_zhu_deng_wang_zhang_li_zhang_lv_liu_zhang_et al._2021, title={High Miscibility Compatible with Ordered Molecular Packing Enables an Excellent Efficiency of 16.2% in All-Small-Molecule Organic Solar Cells}, volume={12}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202106316}, abstractNote={In all‐small‐molecule organic solar cells (ASM‐OSCs), a high short‐circuit current (Jsc) usually needs a small phase separation, while a high fill factor (FF) is generally realized in a highly ordered packing system. However, small domain and ordered packing always conflicted each other in ASM‐OSCs, leading to a mutually restricted Jsc and FF. In this study, alleviation of the previous dilemma by the strategy of obtaining simultaneous good miscibility and ordered packing through modulating homo‐ and heteromolecular interactions is proposed. By moving the alkyl‐thiolation side chains from the para‐ to the meta‐position in the small‐molecule donor, the surface tension and molecular planarity are synchronously enhanced, resulting in compatible properties of good miscibility with acceptor BTP‐eC9 and strong self‐assembly ability. As a result, an optimized morphology with multi‐length‐scale domains and highly ordered packing is realized. The device exhibits a long carrier lifetime (39.8 μs) and fast charge collection (15.5 ns). A record efficiency of 16.2% with a high FF of 75.6% and a Jsc of 25.4 mA cm−2 in the ASM‐OSCs is obtained. These results demonstrate that the strategy of simultaneously obtaining good miscibility with high crystallinity could be an efficient photovoltaic material design principle for high‐performance ASM‐OSCs.}, journal={ADVANCED MATERIALS}, author={Zhang, Lili and Zhu, Xiangwei and Deng, Dan and Wang, Zhen and Zhang, Ziqi and Li, Yi and Zhang, Jianqi and Lv, Kun and Liu, Lixuan and Zhang, Xuning and et al.}, year={2021}, month={Dec} }
 @article{zou_ma_chan_zhang_li_shang_wang_arunagiri_qi_ade_et al._2021, title={Optically Probing Field-Dependent Charge Dynamics in Non-Fullerene Organic Photovoltaics with Small Interfacial Energy Offsets}, volume={125}, ISSN={["1932-7455"]}, DOI={10.1021/acs.jpcc.0c09663}, abstractNote={Current non-fullerene organic photovoltaics (OPVs) can achieve high photocurrent generation yields with small donor/acceptor energy offsets. However, the effect of varying energy offset on the char...}, number={3}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Zou, Xinhui and Ma, Chao and Chan, Christopher C. S. and Zhang, Jianquan and Li, Yunke and Shang, Ao and Wang, Zhen and Arunagiri, Lingeswaran and Qi, Zhenyu and Ade, Harald and et al.}, year={2021}, month={Jan}, pages={1714–1722} }
 @article{yang_fan_wang_yan_dong_cui_ade_li_2020, title={Impact of Isomer Design on Physicochemical Properties and Performance in High-Efficiency All-Polymer Solar Cells}, volume={53}, ISBN={1520-5835}, DOI={10.1021/acs.macromol.0c01405}, abstractNote={Combining the acceptor–donor–acceptor-type fused ring-based molecular architecture into a polymeric backbone is a promising strategy to design polymer acceptors for high-performance all-polymer sol...}, number={20}, journal={MACROMOLECULES}, author={Yang, Hang and Fan, Hongyu and Wang, Zhen and Yan, Hongping and Dong, Yingying and Cui, Chaohua and Ade, Harald and Li, Yongfang}, year={2020}, pages={9026–9033} }
 @article{yu_qi_li_wang_zhou_ade_yan_chen_2020, title={Modulating Energy Level on an A-D-A '-D-A-Type Unfused Acceptor by a Benzothiadiazole Core Enables Organic Solar Cells with Simple Procedure and High Performance}, volume={4}, ISSN={["2367-198X"]}, DOI={10.1002/solr.202000421}, abstractNote={Unfused‐ring acceptors (UFAs) have gained considerable research attention as they offer simple chemical structures through simplified synthesis methods, which would boost the commercialization of organic solar cells (OSCs). Recently, a new small molecule acceptor (SMA) named Y6 was reported, yielding high‐performance OSCs. Herein, the Y6‐like A‐DA′D‐A framework is developed to A‐D‐A′‐D‐A‐type backbone adopted in constructing UFAs. Two new Y6‐like UFAs are synthesized within four steps and the effect of noncovalent atoms at the central electron‐deficient core on material properties and device performances is studied. It is found that the introduction of fluorine atoms can bring larger red‐shift in the absorption spectra and better aggregation of the resulting UFA film states compared with those of oxygen atoms. Interestingly, the variations in the noncovalent interaction atoms induce different intermolecular charge transfer between donors and UFAs. When blended with another economical donor, PTQ10, F substitution at the benzothiadiazole ring is more effective than O substitution, leading to the increased short‐circuit current density (JSC) and higher efficiency of over 12%, among the best performances of UFA‐based OSCs. This contribution demonstrates the appropriate introduction of noncovalent interaction is a promising method for tuning energy levels, absorption, and aggregation of UFAs for high‐performance OSCs.}, number={11}, journal={SOLAR RRL}, author={Yu, Han and Qi, Zhenyu and Li, Xingye and Wang, Zhen and Zhou, Wentao and Ade, Harald and Yan, He and Chen, Kai}, year={2020}, month={Nov} }
 @article{arunagiri_peng_zou_yu_zhang_wang_lai_zhang_zheng_cui_et al._2020, title={Selective Hole and Electron Transport in Efficient Quaternary Blend Organic Solar Cells}, volume={4}, ISSN={["2542-4351"]}, DOI={10.1016/j.joule.2020.06.014}, abstractNote={Multi-component organic solar cells (OSCs) comprising more than two donor and acceptor materials have attracted significant research attention, as they can offer broader and better absorption, hence increasing solar cell performance. However, the morphology of multi-component OSCs is exceptionally complicated and challenging to control. Here, we develop a highly efficient (near 17.7%) quaternary OSC (q-OSC) using two polymer donors (namely PM6 and PTQ10) along with a fullerene (PC71BM) and a non-fullerene acceptor (N3). Our quaternary system demonstrates a new type of “rivers and streams” functional hierarchical (multi-length scale) morphology, where small domains of PTQ10 and PC71BM act as separators that spatially separate PM6 and N3, which effectively suppressed charge recombination, enhanced hole transport, and balanced charge transportation. These improvements in the quaternary system contribute to the increased internal quantum efficiency (IQE) and, thus, lead to an excellent JSC and device performance, which surpass their respective binary and ternary OSCs.}, number={8}, journal={JOULE}, author={Arunagiri, Lingeswaran and Peng, Zhengxing and Zou, Xinhui and Yu, Han and Zhang, Guangye and Wang, Zhen and Lai, Joshua Yuk Lin and Zhang, Jianquan and Zheng, Yan and Cui, Chaohua and et al.}, year={2020}, month={Aug}, pages={1790–1805} }
 @article{yu_qi_zhang_wang_sun_chang_sun_zhou_min_ade_et al._2020, title={Tailoring non-fullerene acceptors using selenium-incorporated heterocycles for organic solar cells with over 16% efficiency}, volume={8}, ISSN={["2050-7496"]}, DOI={10.1039/d0ta06658c}, abstractNote={The selenium substitution strategy was applied to develop two new A′-DAD-A′-type small molecular acceptors. The resulting selenium-incorporated molecules exhibit red-shifted absorption and an enhanced photon response, leading to high device efficiencies of over 16%.}, number={45}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, author={Yu, Han and Qi, Zhenyu and Zhang, Jianquan and Wang, Zhen and Sun, Rui and Chang, Yuan and Sun, Huiliang and Zhou, Wentao and Min, Jie and Ade, Harald and et al.}, year={2020}, month={Dec}, pages={23756–23765} }
 @article{wang_peng_xiao_seyitliyev_gundogdu_ding_ade_2020, title={Thermodynamic Properties and Molecular Packing Explain Performance and Processing Procedures of Three D18:NFA Organic Solar Cells}, volume={32}, ISSN={["1521-4095"]}, DOI={10.1002/adma.202005386}, abstractNote={Organic solar cells (OSCs) based on D18:Y6 have recently exhibited a record power conversion efficiency of over 18%. The initial work is extended and the device performance of D18‐based OSCs is compared with three non‐fullerene acceptors, Y6, IT‐4F, and IEICO‐4Cl, and their molecular packing characteristics and miscibility are studied. The D18 polymer shows unusually strong chain extension and excellent backbone ordering in all films, which likely contributes to the excellent hole‐transporting properties. Thermodynamic characterization indicates a room‐temperature miscibility for D18:Y6 and D18:IT‐4F near the percolation threshold. This corresponds to an ideal quench depth and explains the use of solvent vapor annealing rather than thermal annealing. In contrast, D18:IEICO‐4Cl is a low‐miscibility system with a deep quench depth during casting and poor morphology control and low performance. A failure of ternary blends with PC71BM is likely due to the near‐ideal miscibility of Y6 to begin with and indicates that strategies for developing successful ternary or quaternary solar cells are likely very different for D18 than for other high‐performing donors. This work reveals several unique property–performance relations of D18‐based photovoltaic devices and helps guide design or fabrication of yet higher efficiency OSCs.}, number={49}, journal={ADVANCED MATERIALS}, author={Wang, Zhen and Peng, Zhengxing and Xiao, Zuo and Seyitliyev, Dovletgeldi and Gundogdu, Kenan and Ding, Liming and Ade, Harald}, year={2020}, month={Dec} }