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 (PbCl2) 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. [Display omitted] •DMSO/DMF promoted directional growth of PbICl crystals into “rod-like” precursors.•DMSO/DMF induced formation and storage of amorphous PbCl2 in perovskite films.•High-performance and non-hysteresis planar heterojunction PSCs were achieved.