Spiro-Linked Planar Core Small Molecule Hole Transport Materials Enabling High-Performance Inverted Perovskite Solar Cells
Zhixin Liu, Jie Zeng, Deng Wang, Peide Zhu, Lida Wang, Yitian Bao, Yintai Xu, Wenbo Peng, Siru He, Zhiwei Lei, L. Y. Pang, Bo Jiang, Jiangfeng Wang, Zonglong Song, Yong Zhang, Xingzhu Wang, Lei Yan, Baomin Xu
Abstract
Small-molecule organic semiconductors have demonstrated significant potential for application in hole-transporting materials (HTMs) for perovskite solar cells (PSCs), thanks to their high reproducibility and convenient synthesis routes. Finely designed planar π–π stacking structures have emerged as one of the primary strategies for achieving high-performance small-molecule HTMs. In particular, the incorporation of a helical structure into HTM designs through a linearization approach has proven effective, leading to the development of novel materials with superior properties. In this study, the structure–property relationship of these small molecules has been systematically explored. The newly developed HTM, SPCF-MeTPA, based on a spiro[cyclopentane-1,9′-fluorene] core, features a rigid conjugated system with spiro-linked core. This design provides improved intermolecular charge extraction and transport, optimized energy levels, and effective surface passivation compared to SPTP-MeTPA, which has a nonplanar spatial arrangement. As a result, the champion device based on SPCF-MeTPA achieves efficiencies of 26.35% (certified 25.75%) and 24.55% for aperture areas of 0.07 and 1.01 cm 2, respectively. Additionally, these devices demonstrate exceptional long-term stability, further highlighting the potential of SPCF-MeTPA as a high-performance HTM.