Quantum Dot Enabled Cation Exchange in Halide Perovskites for Photovoltaics and Infrared Photodetectors

Tailoring the photophysical properties of halide perovskites is a promising strategy to simultaneously address defects, modulate carrier dynamics, and expand the spectral response. Quantum dots (QDs) are promising candidates to functionalize perovskites; however, the interaction mechanisms between robust-lattice QDs and ionic perovskites remain unclear. Here, we pioneer a cation exchange approach using CdSe QDs to functionalize lead halide perovskites, where Cd²⁺ replaces Pb²⁺ and diffuses throughout the perovskite matrix. This cation exchange achieves dual benefits: (1) efficient defect passivation via Cd^2- diffusion and Se^2- coordination with undercoordinated Pb²⁺, and (2) extended infrared light response up to 1200 nm attributed to in situ formed PbSe QDs. The champion perovskite solar cells delivered a power conversion efficiency of 24.8%, significantly outperforming the control devices (23.0%). Moreover, infrared PbSe QDs formed enable broadband detection to infrared spectrum (300-1200 nm), with a detectivity of 2.9 × 10¹¹ Jones at 1170 nm under −0.3 V bias. Extension of this strategy to CdS QDs further confirmed this cation exchange mechanism. Therefore, our work establishes a versatile, scalable interface-engineering method between robust-lattice QDs and perovskites, paving the way for multifunctional optoelectronic applications.