Grain Growth of MAPbI3 via Diethylammonium Bromide Induced Grain Mergence

Various additives are used to improve the film morphology, crystal quality, and grain size for the sake of enhancing the performance of three-dimensional perovskite solar cells. Although significant enhancement in the performance of devices has been made due to the introduction of additives, an in-depth understanding of the additive-related crystallization kinetics and the growth mechanism is still lacking. Here, the grain growth mechanism of diethylammonium bromide (DABr)-doped MAPbI(3) is investigated using in situ dynamic microscopy techniques. The results reveal that the alkyl chains of DABr restrain the growth of grains of MAPbI(3) during spin-coating, and DABr-induced grain mergence during the annealing process, achieving large grains on the micrometer scale. Meanwhile, the crystallization of MAPbI(3) with DABr is significantly improved and the number of defects is reduced. The solar cell with optimized DABr doping MAPbI(3) as the active layer presents a higher power conversion efficiency (PCE) of 19.58% with a fill factor of 79.81%.