Suppressing Excess Lead Iodide Aggregation and Reducing N‐Type Doping at Perovskite/HTL Interface for Efficient Perovskite Solar Cells

Abstract Excess lead iodide (PbI 2 ) aggregation at the charge carrier transport interface leads to energy loss and acts as unstable origins in perovskite solar cells (PSCs). Here, a strategy is reported to modulate the interfacial excess PbI 2 by introducing π ‐conjugated small‐molecule semiconductors 4,4'‐cyclohexylbis[N,N‐bis(4‐methylphenyl)aniline] (TAPC) into perovskite films through an antisolvent addition method. The coordination of TAPC to PbI units through the electron‐donating triphenylamine groups and π ‐Pb 2+ interactions allows for a compact perovskite film with reduced excess PbI 2 aggregates. Besides, preferred energy level alignment is achieved due to the suppressed n‐type doping effect at the hole transport layer (HTL) interfaces. As a result, the TAPC‐modified PSC based on Cs 0.05 (FA 0.85 MA 0.15 ) 0.95 Pb(I 0.85 Br 0.15 ) 3 triple‐cation perovskite achieved an improved PCE from 18.37% to 20.68% and retained ≈90% of the initial efficiency after 30 days of aging under ambient conditions. Moreover, the TAPC‐modified device based on FA 0.95 MA 0.05 PbI 2.85 Br 0.15 perovskite produced an improved efficiency of 23.15% compared to the control (21.19%). These results provide an effective strategy for improving the performance of PbI 2 ‐rich PSCs.