Emerging hole transport layers for PbS quantum dot solar cells and photodetectors

Lead sulfide quantum dot (PbS QD) optoelectronic devices, notably infrared solar cells and short-wave infrared photodetectors, are ready to drive next-generation optoelectronics due to their tunable optoelectronic properties and solution processability. In high-performance PbS QD devices, QDs serve dual roles as the active layer and hole transport layer (HTL), leveraging their favorable energy level alignment and wide bandgap characteristics. However, HTLs using ethanedithiol-treated PbS QDs (PbS–EDT) are vulnerable to humidity and air exposure, which accelerates performance degradation through interfacial recombination driven by deteriorating ligand exchange. Herein, we review recent advancements in HTL engineering aimed at mitigating trap recombination and enhancing device stability. Novel ligand exchange strategies for p-type QDs, alongside alternative organic, inorganic, and hybrid HTL materials, are systematically evaluated. These innovations have significantly improved the stability and efficiency of PbS QD-based photodiodes, including solar cells and photodetectors. By elucidating these developments, this study offers critical insights and strategic directions for designing high-performance, stable PbS QD optoelectronic devices for future research and applications.