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Nonhalogenated Solvent-Processed All-Polymer Solar Cells over 7.4% Efficiency from Quinoxaline-Based Polymers

Zhou, Liuyang, He, Xuan, Lau, Tsz-Ki, Qiu, Beibei, Wang, Tao, Lu, Xinhui, Luszczynska, Beata, Ulanski, Jacek, Xu, Shutao, Chen, Guohui, Yuan, Jun, Zhang, Zhi-Guo, Li, Yongfang, Zou, Yingping
ACS applied materials & interfaces 2018 v.10 no.48 pp. 41318-41325
absorbance, additives, ambient temperature, chloroform, dissociation, polymers, separation, solar cells, solvents, tetrahydrofuran
Two conjugated polymers, with different side chains of alkoxy-substituted difluorobenzene and alkyl-substituted difluorobenzene based on quinoxaline (Qx) as the electron acceptor unit and benzodithiophene as the electron donor unit, named HFQx-T and HFAQx-T, were used as electron donor polymers to fabricate all-polymer solar cells (all-PSCs) with a naphthalenediimide–bithiophene n-type semiconducting polymer (N2200). Usually, halogenated solvents are harmful to natural environment and human beings, and solvent additives were disadvantageous in the process of roll-to-roll technology. The Qx-based polymers are successfully used to fabricate high-performance all-PSCs, which processed with the nonhalogenated solvent tetrahydrofuran (THF) at room temperature. With THF as the processing solvent, the active layer showed a higher absorption coefficient, better phase separation, exciton dissociation, and charge carrier mobilities than that processed with CHCl₃. Moreover, the photovoltaic properties have been dramatically improved with THF. The optimized device of HFAQx-T:N2200 processed with THF delivered an efficient power conversion efficiency (PCE) of 7.45%, which is the highest PCE for all-PSCs from Qx-based polymers processed by a nonhalogenated solvent.