A Triple Axial Chirality, Racemic Molecular Semiconductor Based on Thiahelicene and Ethylenedioxythiophene for Perovskite Solar Cells: Microscopic Insights on Performance Enhancement

• Published in: Advanced functional materials 2021-04, Vol.31 (16), p.n/a
• Main Authors: Zheng, Aibin, Xie, Xinrui, Wang, Yiming, Xu, Niansheng, Zhang, Jing, Yuan, Yi, Wang, Peng
• Format: Article
• Language: English
• Subjects: Chirality; Energy levels; glass transition; Glass transition temperature; helicene; Materials science; molecular modeling; Morphology; organic semiconductor; Perovskites; Photovoltaic cells; Semiconducting films; Solar cells; Temperature; Thermal stress; Translational motion
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202009854

For the low‐cost fabrication of large‐area, durable perovskite solar cells, it is of pivotal importance to engineer organic semiconducting films with a combined property of matched energy level, sufficiently large conductivity, high glass transition temperature, and excellent solution processability. Toward this goal, herein an in silico tailored molecular semiconductor (T5HE‐OMeTPA) with triple axial chirality, by joint use of thia[5]helicene and ethylenedioxythiophene, is reported. T5HE‐OMeTPA with a reduced reorganization energy of hole transfer can be exploited as the hole transport layer for perovskite solar cells with 21% efficiency, which also display excellent long‐term stability at 60 °C. The doped, sufficiently conductive T5HE‐OMeTPA composite with a glass transition temperature of 121 °C not only exhibits persistent film morphology under thermal stress, but also surprisingly damps the motion of diffusive components of perovskite for a better control of the degradation of photoactive layer. The translational motion of both ions and molecules is intrinsically associated with the glass transition of a doped molecular semiconductor composite, which is in stark contrast to the microscopic fashion for the glass transition of an undoped molecular semiconductor, that is, thermally activated rotation of diphenylamine. A triple axial chirality, high glass transition temperature, racemic molecular semiconductor based on thiahelicene and ethylenedioxythiophene is used as hole transport material for 21%‐efficiency, 60 °C stable perovskite solar cells. The high glass transition temperature molecular semiconductor damps the motion of the diffusive perovskite component for better control of perovskite decomposition.