Role of DMSO concentration in the crystallization process of MAPbBr3 perovskite single crystal films

Halide perovskite single-crystal films have attracted significant attention due to their extraordinary performance in various optoelectronic applications such as solar cells, light-emitting devices, photodetectors, and X-ray detectors. However, the surface quality and crystallinity of perovskite single crystal films (PSCFs) prepared by the popular space-confined method limits the applications in the high-performance devices. Herein, we demonstrate a simple method to improve the crystallinity of MAPbBr3 PSCFs by introducing dimethylsulfoxide (DMSO) as the coordination solvent into the precursor solutions. When increasing the DMSO concentration in the perovskite precursor solutions, the precipitation of lead bromide on the surface of PSCFs is suppressed. The best MAPbBr3 PSCF obtained at 2.5% DMSO concentration has a full width at half maximum (FWHM) of 0.0042° in the X-ray rocking curve measurements, which is significantly improved compared with the best published results. The mechanism how DMSO concentration affect the crystallization process and the formation of defects is also discussed. The study provides an effective route to fabricate perovskite single crystal films and inspires further explorations on the production of high-performance optoelectronic devices.