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

Excess lead iodide (PbI₂) 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 PbI₂ 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-Pb²⁺ interactions allows for a compact perovskite film with reduced excess PbI₂ 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_0.85MA_0.15)_0.95Pb(I_0.85Br_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_0.95MA_0.05PbI_2.85Br_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 PbI₂-rich PSCs.