Temperature-assisted rapid nucleation: a facile method to optimize the film morphology for perovskite solar cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c7ta06334b

The nucleation stage has an important influence on the lead halide perovskite film morphology, and therefore the solar cell performance. Here, we introduce a facile temperature-assisted rapid nucleation (TRN) method to improve the film crystallization process and the film morphology. By employing low temperature anti-solvents (diethyl ether, chlorobenzene and toluene), we stimulate homogeneous nuclei growth, resulting in a highly dense perovskite thin layer. The TRN method prepared (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 devices exhibit a power conversion efficiency up to 19.2% and maintain over 85% of the original efficiency after 40 days of storage at room temperature under a relative humidity of 10-40%. The nucleation stage has an important influence on the lead halide perovskite film morphology, and therefore the solar cell performance.