Dual Interface Passivation in Mixed-Halide Perovskite Solar Cells by Bilateral Amine

Poor crystallization and nonradiative recombination at charge transfer interfaces are the main challenges in scaling up mixed-halide perovskite solar cells. If the theoretical open-circuit voltage (VOC) limit is to be achieved, surface defects at the perovskite surface and grain boundaries must be suppressed by passivation. However, it is unavoidable that the passivation material will strongly bind to the perovskite without disrupting the three-dimensional (3D) symmetry. When primary amines are introduced into perovskite precursors, they generate a quasi-2D/3D perovskite with poor photocurrent charge transport properties. To address these constraints, we show that secondary amine (N,N '- dimethyl-1,3-propanediammonium dichloride) can stabilize the bulk phase of perovskite materials, passivating both surfaces and improving the charge carrier lifetime. In particular, a record-high VOC of 1.27 V is achieved at an optimal band gap of 1.63 eV. Our findings will help to guide future efforts to improve the performance and stability of perovskite solar cells.