Stable and Efficient Inverted Perovskite Solar Cells Enabled by Structural Design of Lewis Base Molecules

Lewis base molecules are capable of binding undercoordinated Pb2+ at the interface and grain boundaries, effectively modifying the interfacial defects and thus improving the durability of metal halide perovskite solar cells (PSCs). In this study, we independently designed two innovative materials with strong binding energy as Lewis base molecules: 2-(1-methylpiperidin-1-ium-1-yl)-1-phenylethanone (M1) and 2-(4-methylmorpholin-4-ium-4-yl)-1-phenylethanone (M2). Using density functional theory (DFT) calculations, we found that the electron-donating ability of the C=O bond in M2 is stronger than that in M1. We experimentally determined that the M2 passivated MAPb(I0.97Br0.03)3 thin films exhibit excellent morphology with a more uniform surface and improved crystallinity, thus suppressing nonradiative recombination. The PSC based on M2-passivated MAPb(I0.97Br0.03)3 thin film showed the maximum power conversion efficiency of 21.80%, which is much higher than that of PSCs based on M1-passivated MAPb(I0.97Br0.03)3 thin film and MAPb(I0.97Br0.03)3 thin film, while exhibiting a high fill factor (FF) of 82.53% and long-term stability in the air atmosphere (45% RH).