A facile deposition of large grain and phase pure α-FAPbI3 for perovskite solar cells via a flash crystallization

The alpha-HC(NH2)(2)PbI3 (FAPbI(3)) perovskite with narrower band gap and higher thermal stability is a promising candidate for high performance perovskite optoelectronic applications. However, it is difficult to achieve fast growth of a phase pure alpha-FAPbI(3) perovskite because the unwanted delta-FAPbI(3) usually first forms at lower temperature then converted into the wanted alpha-FAPbI(3) at higher temperature. It takes long time annealing to complete the conversion of delta-FAPbI(3) to alpha-FAPbI(3), which could also lead to uncontrollable degradation of alpha-FAPbI(3). Here we report a facile flash deposition of large grain phase pure alpha-FAPbI(3) without any delta-FAPbI(3) impurity by inhibiting the delta phase crystallization. In this method, a simple PMMA sealing to synchronize a flash alpha-crystallization process at appropriate temperature with the unwanted delta phase crystallization. Consequently, a high quality phase pure alpha-FAPbI(3) with large grain size was fabricated into high performance perovskite solar cells. The strategy of flash crystallization would be a promising method for deposition of phase pure perovskite in future. (C) 2017 Elsevier Ltd. All rights reserved.