Combined solvent and vapor treatment to prepare high quality perovskite films under high relative humidity

It is a great challenge to prepare high quality perovskite films in ambient atmosphere with high humidity (≥   50%), since the commonly adopted two step sequential deposition process produces perovskite films with rough surfaces and a large amount of residual PbI 2 . To solve these problems, a facile method using combined solvent and vapor treatment is proposed. The residual PbI 2 is diminished through a solvent treatment process, and then smooth perovskite surface with micrometer scaled perovskite particles is obtained with a CH 3 NH 2 vapor treatment. The quality of the obtained perovskite films is examined in the hole transport material free perovskite solar cells, and power conversion efficiency is boosted up by 17.3% compared with the traditional method. When a CuPc hole transport layer is further introduced, carbon counter electrode based perovskite solar cells exhibit a superior power conversion efficiency of 16.61%. Thus this method shows great potential in further optimizing the performance of perovskite solar cells.