Novel insights into the role of solvent environment in perovskite solar cells prepared by two-step sequential deposition

We use a two-step spin-coating method to construct efficient and non-hysteresis planar perovskite solar cells (PSCs). The influence of solvent environment on the precursor configuration, perovskite crystallization kinetics , and photoelectric properties of the PSCs are systematically studied, resulting in novel insights into the function of dimethyl sulfoxide/dimethylformamide (DMSO/DMF) blend solvent (BS). The DMSO/DMF BS promotes the construction of porous “rod-like” precursor film, which provides sufficient space for lattice expansion and orientation selection during perovskite growth, thus producing high-quality perovskite absorbers with high crystallinity . Moreover, DMSO/DMF BS also induces the formation of amorphous lead chloride (PbCl 2 ) and stores it in the final perovskite film, effectively passivating perovskite defects, extending carrier lifetime, and significantly improving device performance. As a result, a DMSO/DMF-based planar PSC is prepared with reverse efficiency of 19.69% and forward efficiency of 19.54%. Moreover, devices show a good stability over 500 h and reproducibility in 20 pieces fabricated with the same procedure. This study provides a new concept for the preparation of high-quality perovskite absorbers and highly efficient planar PSCs, and represents an important contribution toward determining the potential influence of solvent engineering on perovskite crystallization kinetics.