sec-Butyl alcohol assisted pinhole-free perovskite film growth for high-performance solar cells

Perovskites have recently emerged as promising materials for high-performance, low-cost photovoltaic devices. Here, we report a one-step, solvent-induced, fast crystallization method based on sec-butyl alcohol to produce flat, uniform CH3NH3PbI3 films. sec-Butyl alcohol has proven to be a suitable solvent not only for the CH3NH3PbI3 fast crystallization deposition process, but also for adjusting the amount of CH3NH3I in CH3NH3PbI3 films. Planar heterojunction solar cells with flat and pinhole-free CH3NH3PbI3 films yielded an average power conversion efficiency (PCE) of 13.1 +/- 1.2% and the highest PCE of 14.3%; no hysteresis was observed by changing the scan direction in our devices under standard AM 1.5 illumination. Remarkably, we found that the presence of CH3NH3I in CH3NH3PbI3 films has a positive effect on the photovoltaic device performance.