Simple post annealing-free method for fabricating uniform, large grain-sized, and highly crystalline perovskite films

We report a simple post annealing-free (PAF) method for making uniform, large grain-sized, and highly crystalline triple cation perovskite films. In this simple process, a perovskite precursor solution was spin-coated onto a TiO2 mesoporous substrate and as an antisolvent, diethyl ether (DEE) was subsequently dripped onto the film during spinning to produce an intermediate phase (IP) of perovskite film. This IP was immediately immersed into a DEE bath at room temperature for only 1 min in replacement of the conventional post annealing (PA) treatment. The as-prepared PAF film was characterized by X-ray powder diffraction, UV vis absorption spectroscopy, fourier transform infrared spectroscopy, scanning electron microscopy, atomic-force microscopy, and photoluminescence spectroscopy. The overall power conversion efficiency (PCE) of the PAF devices was in the range of 18.8-19.5%, which is comparable with the reported PA devices (17.2-18.1%), mainly due to the J(SC) and the FF values, caused by the high absorption ability and the large crystal size with better surface smoothness in the PAF film. This efficiency is the highest reported for perovskite deposition by PAF methods. This new method enables reducing the device fabrication time at room temperature, which will reduce the cost of manufacturing efficient perovskite solar cells.