Competing ion effect in the crystal solution and thin films of 2D organic-spacer-incorporated 3D perovskites

Abstract

We prepared quasi-2D perovskites using the co-spacers guanidium (GA) + ethylammonium (EA) and GA + imidazolium (IM) by forming crystals in solution and thin films for solar cells. Compared with the perovskite crystal prepared using only one spacer in solution, the crystal structure was completely different when prepared using two spacers. We investigated the mechanism of film formation from the dominant single crystal in solution because it plays the main role in crystal growth. The use of multiple ion spacers in the formation of perovskite films induces a decrease in nonradiative recombination and trap density, thus improving conductivity and carrier lifetimes. Through the optimization of multiple spacer compositions, EA_0.07GA_0.03MA_0.9PbI₃- and IM_0.05GA_0.05MA_0.9PbI₃-based devices achieved the highest power conversion efficiency (PCE) of 17.31% and 17.83%, respectively. This work provides an efficient strategy to prepare high-quality perovskite films by introducing multiple spacers into a perovskite lattice, which reduces defect trap density and improves crystallinity, resulting in high-efficiency perovskite solar cells.