Interface Regulation via Tailored Multifunctional Small Molecule toward Efficient Perovskite Solar Cells

Abstract Optimizing the interfacial charged traps in perovskite films is essential to reduce non‐radiative recombination and improve the optoelectronic performance of perovskite solar cells. Herein, small molecules with varying active sites and spatial configurations are designed to modulate the deep‐level defects and non‐radiative recombination of the perovskite interface. 2,3,5,6‐tetrabromo‐N1,N4‐bis(2‐octyldodecyl)terephthalamide (PA‐4Br) with four symmetrical Br atoms exhibits the optimal spatial arrangement to eliminate interfacial defects. Experimental and theoretical results reveal that the amide and Br atoms in PA‐4Br have a synergistic effect with the uncoordinated Pb²⁺, and they not only effectively eliminate interface defects and inhibit non‐radiative recombination but also substantially improve the interface energy level arrangement and facilitate interface charge transfer efficiency, finally achieving a champion power conversion efficiency of 25.50% with an impressive fill factor of 84.22%, together with excellent maximum‐power‐point (MPP) tracking stability.