CsPbI2Br epitaxial shell for efficient PbS quantum dot solar cells

Lead sulfide quantum dots (PbS QDs) are promising candidates for high-performance solar cells due to their tunable bandgaps and low-cost solution processing. However, low carrier mobility and numerous surface defects restrict the performance of the fabricated solar cells. Herein, we report the synthesis of novel PbS-perovskite core-shell QDs to solve the low carrier mobility problem of PbS QDs via a facile hot injection method. CsPbI2Br shell enabled strain-free epitaxial growth on the surface of PbS QDs because of 98% lattice match. Our results demonstrate a significant improvement in the photoluminescence and stability of the synthesized PbS-CsPbI2Br QDs upon shell formation, attributed to the effective suppression of surface defects by the epitaxial shell of CsPbI2Br. As a result, the obtained solar cell based on PbS-CsPbI2Br core-shell QD exhibits a power conversion efficiency (PCE) of 8.43%, two times higher than that of pristine PbS QDs. Overall, the construction of PbS-CsPbI2Br core-shell structures represent a promising strategy for advancing the performance of PbS QDs-based optoelectronic devices.