Room-temperature water-vapor annealing for high-performance planar perovskite solar cells

Abstract

We report here the discovery of a unique room-temperature water-vapor annealing (WVA) method to fabricate high performance planar heterojunction perovskite solar cells (pero-SCs) based on CH₃NH₃PbI₃. High crystallinity and void-free perovskite films were obtained by the WVA treatment at room temperature without thermal annealing (TA) and the power conversion efficiency (PCE) of the pero-SCs reached 16.4% with a high open circuit voltage (V_oc) of 1 V. A mechanism is proposed that the water vapor molecules catalyzed the dissolution and re-crystallization of the perovskite at the grain edges and void area, resulting in void-free and large sized crystals in the perovskite films and the improved photovoltaic performance. This WVA approach provides a simple, high-efficiency and energy conservation processing method in the fabrication of planar perovskite solar cells towards commercialization.