Improvement of Colloidal Characteristics in a Precursor Solution by a PbI2-(DMSO)2 Complex for Efficient Nonstoichiometrically Prepared CsPbI2.8Br0.2 Perovskite Solar Cells

The optoelectronic properties of all-inorganic perovskite solar cells are greatly affected by the quality characteristics of films, such as the defect concentration, crystal growth orientation, crystallinity, and morphology. In this study, a PbI2-(DMSO)(2) complex is adopted to partially replace PbI2 as the lead source in the preparation of perovskite precursor solutions. Due to the rapid dispersion of the PbI2-(DMSO)(2) complex in a solvent, raw materials can rapidly react to form perovskite colloids with a narrow size distribution. Such uniform colloidal particles are found to be beneficial for achieving films with improved quality and highly orientated growth along the [001] direction. The optimized film exhibits a clearly improved crystallinity and a decrease in defect concentration from 4.29 x 10(15) cm-3 to 3.20 x 10(15) cm(-3). The device based on the obtained all-inorganic CsPbI2.8Br0.2 perovskite finally achieves an increase in photovoltaic power conversion efficiency from 10.5 to 14.15%. In addition, the environmental stability of the device also benefits from the improved film quality. After 480 h of storage in air, the device can still maintain nearly 80% of its initial performance.