Synergistical Dipole–Dipole Interaction Induced Self‐Assembly of Phenoxazine‐Based Hole‐Transporting Materials for Efficient and Stable Inverted Perovskite Solar Cells
Ning Cai, Fengzhu Li, Yatong Chen, Ruixi Luo, Tonghui Hu, Francis Lin, Shek‐Man Yiu, Danjun Liu, Dangyuan Lei, Zonglong Zhu, Alex K.‐Y. Jen
Abstract
Delicately designed dopant-free hole-transporting materials (HTMs) with ordered structure have become one of the major strategies to achieve high-performance perovskite solar cells (PSCs). In this work, we report two donor-π linker-donor (D-π-D) HTMs, N01 and N02, which consist of facilely synthesized 4,8-di(n-hexyloxy)-benzo[1,2-b:4,5-b']dithiophene as a π linker, with 10-bromohexyl-10H-phenoxazine and 10-hexyl-10H-phenoxazine as donors, respectively. The N01 molecules form a two-dimensional conjugated network governed by C-H⋅⋅⋅O and C-H⋅⋅⋅Br interaction between phenoxazine donors, and synchronously construct a three-dimension lamellar structure with the aid of interlaminar π-π interaction. Consequently, N01 as a dopant-free small-molecule HTM exhibits a higher intrinsic hole mobility and more favorable interfacial properties for hole transport, hole extraction and perovskite growth, enabling an inverted PSC to achieve a very impressive power conversion efficiency of 21.85 %.