Record‐Efficiency Printable Hole‐Conductor‐Free Mesoscopic Perovskite Solar Cells Enabled by the Multifunctional Schiff Base Derivative

Abstract Tailoring multifunctional additives for performing interfacial modifications, improving crystallization, and passivating defects is instrumental for the fabrication of efficient and stable perovskite solar cells (PSCs). Here, a Schiff base derivative, (chloromethylene) dimethyliminium chloride (CDCl), is introduced as an additive to modify the interface between the mesoporous TiO₂ electron transport layer and the MAPbI₃ light absorber during the annealing process. CDCl chemically links to TiO₂ and MAPbI₃ through coordination and hydrogen bonding, respectively, and results in the construction of fast electron extraction channels. CDCl also optimizes the energy‐level alignment of the TiO₂/MAPbI₃ heterojunction and improves the pore‐filling and crystallization of MAPbI₃ in the mesoscopic scaffold, which inhibits nonradiative recombination and eliminates open‐circuit voltage losses. As a result, an impressive power conversion efficiency of 19.74%, which is the best one ever reported, is obtained for printable carbon‐based hole‐conductor‐free PSCs based on MAPbI₃.