Inorganic Ligands Boosted Hybrid Infrared Photodetection via Energy Level Alignment and Interface Charge Transfer

Abstract

Surface ligands do not merely enhance the environmental stability of quantum dots (QDs) but also exert a profound influence on their photoelectric characteristics. Short-chain ligands facilitate interfacial electrical coupling between QD, thereby significantly enhancing the capture and transport of charge carriers under photoexcitation in photodetectors. The impact of ligand properties on charge transport has been widely elucidated, while the critical role of inorganic ligand energy levels in the transfer and recombination of photogenerated carriers remains insufficiently investigated. In this study, different metal chalcogenides are employed as ligands to enhance the performance of the PbS QDs-graphene hybrid photodetectors. The responsivity of hybrid devices modified by Na₃AsS₄ ligand is enhanced by an order of magnitude compared to the Na₄SnS₄ ligand-modified devices. The highest occupied molecular orbital (HOMO) energy level of the Na₃AsS₄ ligand and the valence band of the QDs exhibit a smaller energy difference compared to those of the Na₄SnS₄ ligand, which significantly enhances the capture and transfer efficiency of photogenerated holes. The results underscore the essential role of inorganic ligands, providing important implications for the future development of high-performance optoelectronic devices utilizing ligand-modified QDs.