Solution-Processable Chlorostannylene Complexes as Surface Modifiers for Tin Halide Perovskite Solar Cells

Surface modification by excess tin ions is an effective passivation method for defects in tin perovskite films. However, the low solubility of tin halides in nonpolar solvents makes the implementation difficult. In this study, a solution-processable source of tin halide, the divalent organotin species (9-triptycyl)chlorostannylene, was synthesized. While initially isolated as a cyclic pentamer, this compound was successfully converted into monomeric units through complexation with pyridine. When applied as a surface passivation agent for tin perovskite films, the pyridine-complexed monomers could enhance the performance of tin perovskite solar cells. The open-circuit voltage increased from 0.56 to 0.65 V, translating to an overall power conversion efficiency increase from 9.3 to 10.5%.