Core-twisted tetrachloroperylenediimide additives improve the crystallinity of perovskites to provide efficient perovskite solar cells

Defects at the grain boundaries and surfaces of metal-halide perovskite films function as non-radiative recombination centers that decrease the performance and/or stability of perovskite solar cells (PSCs). The incorporation of additives into perovskite films can improve their quality and, thereby, provide high-performance PSCs. In this study, we introduced core-twisted tetrachloroperylene diimide (ClPDI) derivatives (n-type small molecules) into the lead iodide precursor solution and used a two-step deposition method to prepare methyl ammonium lead triiodide (MAPbI(3)) perovskite films. We examined the effects of the terminal functional groups of the ClPDI derivatives-n-butyl (ClPDI-C4), dimethylaminopropyl (ClPDI-C3DMeA), and aminopropyl (ClPDI-DPA) - on their ability to control the crystallization rate and modulate the film morphology. The power conversion efficiency of the PSC prepared without an additive (15.88%) improved to 16.88 and 18.77% after incorporation of ClPDI-C4 and ClPDI-DPA, respectively, because the strong interactions between these additives and the perovskite passivated defects, slowed the rate of perovskite crystal growth, and increased the grain size. Thus, the use of ClPDI additives in perovskite films can effectively enhance both the efficiency and stability of PSCs.