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Dopant-Free Hole-Transporting Polycarbazoles with Tailored Backbones for Efficient Inverted Perovskite Solar Cells

Xie, Yuanyuan, Wang, Xuxian, Chen, Qing, Liu, Sizhou, Yun, Yikai, Liu, You, Chen, Cheng, Wang, Jungan, Cao, Yezhou, Wang, Fangfang, Qin, Tianshi, Huang, Wei
Macromolecules 2019 v.52 no.12 pp. 4757-4764
cations, engineering, polymers, solar cells
Three conjugated polymers based on different linkage sites of carbazole repeat units, 3,6-PCzTPA, 2,7-PCzTPA, and 3,6-2,7-PCzTPA, were obtained through judicious molecular engineering. We observed that structure differences between 2,7- and 3,6-carbazole linkage sites could significantly influence intra- and intermolecular architectures and electronic states of materials. Herein, 3,6-PCzTPA and 3,6-2,7-PCzTPA with 3,6-carbazole units exhibited higher hole mobilities owing to the formation of radical cations, compared to 2,7-PCzTPA with 2,7-carbazole units. As a result, by using 3,6-2,7-PCzTPA as the hole-transporting material, perovskite solar cells with the p–i–n structure demonstrated the highest power conversion efficiency up to 18.4%. The outstanding device performance originated from compositive values of open-circuit voltage and fill factor, which were attributed to the suitable energy level as well as a high hole mobility of 3,6-2,7-PCzTPA. Moreover, its straightforward synthesis strategy, fine film-formation ability, and nondopant requirement indicated 3,6-2,7-PCzTPA as an ideal hole-transporting material for perovskite solar cells.