Size-tunable MoS2 nanosheets for controlling the crystal morphology and residual stress in sequentially deposited perovskite solar cells with over 22.5% efficiency

The two-step crystallization method for perovskite film fabrication has been recognized as an efficient process to obtain high-performance perovskite solar cells (PSCs). However, many issues related to the as-prepared lead iodide (PbI2) film have often been reported. Here, molybdenum disulfide (MoS2) nanosheets with optimized width and thickness via a hydrothermal synthetic method were incorporated into the PbI2 precursor solution, functioning as nano-scaffolds to delay the quick nucleation process of PbI2 and expand the physical volume of the PbI2 film with a nanoporous skeleton morphology. As a result, the penetration of the organic iodide is greatly improved, leading to an optimized surface perovskite crystal orientation with substantially reduced residual stress and trap density. Finally, a champion power conversion efficiency of 22.50% was realized by the MoS2-treated PSCs with improved stability, maintaining 87% of the original performance after 1200 h of ambient storage, 89% of the original performance after 600 h of thermal aging, and 85.1% of the original performance after 73 h of light-soaking aging. This work provides a new way to regulate the two-step crystallization process for fabricating high-performance and stable planar PSCs.

Automated summary

The two-step crystallization method for perovskite film fabrication has been improved by incorporating MoS2 nanosheets as nano-scaffolds. The MoS2 treatment enhances the penetration of organic iodide, improves crystal orientation, and reduces residual stress and trap density in the film. The resulting PSCs exhibit high conversion efficiency and stability.