High Performance of Perovskite Solar Cells via Catalytic Treatment in Two-Step Process: The Case of Solvent Engineering

Currently, the potential mechanism of the solvent-assisted crystallization for mixed cations perovskite thin film (FAxMA1-xPbI3) prepared via two-step solution-process still remains obscure. Here, we clarified the molecular-competing-reacted process of NH2CH═NH2I (FAI) and CH3NH3I (MAI) with PbI2(DMSO)x complex in dimethyl sulfoxide (DMSO) and diethyl ether (DE) catalytic solvent system in the sequential two-step solution-process. The microscopic dynamics was characterized via the characterizations of in situ photoluminescence spectra. In addition, we found that the thermal stability of the perovskite films suffered from the residual solvent with high boiling point, for example, DMSO. The further DE treatment could promote the volatility process of DMSO and accelerate the crystallization process of perovskite films. The highest PCE over 19% with slight hysteresis effect was eventually obtained with a reproducible FA0.88MA0.12PbI3 solar cell, which displayed a constant power output within 100 s upon light soaking and stable PCE output within 30 d in the thermal stability test.