Indoline‐Based Dopant‐Free Hole Transporting Material with Edge‐on Orientation for High Performance Perovskite Solar Cells

Molecular stacking and orientation are of great importance in regulating optoelectronic properties. Typically, the face‐on orientation of hole transporting materials (HTMs) is considered to be a prerequisite for the realization of high efficiency perovskite solar cells (PSCs). Herein, a small molecule HTM, BDT‐ p ‐IDN, is developed with edge‐on orientation by replacing the terminal group from diphenylamine to indoline unit. Remarkably, the PSCs device based on dopant‐free BDT‐ p ‐IDN exhibits an efficiency of 23.28%, which is comparable to that of its face‐on control BDT‐DPA‐F. Compared to BDT‐DPA‐F, BDT‐ p ‐IDN has stronger interaction with the perovskite (PVK) film and therefore stronger hole extraction and defect passivation capabilities, resulting in an increased short circuit current density and improved efficiency. The results indicate that edge‐on orientation could be a powerful way for HTMs to realize efficient PSCs.