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

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. A record power conversion efficiency of 19.74% is achieved for the printable hole‐conductor‐free carbon‐based mesoscopic perovskite solar cell by introducing the multifunctional additive of (chloromethylene) dimethyliminium chloride (CDCl). As a Stiff base derivative, CDCl interacts well with TiO2 and perovskite, which induces modulated energy level alignment and enhanced crystallinity of perovskite in mesopores for the enhanced device performance.