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 × 10¹⁵ cm–³ to 3.20 × 10¹⁵ 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.