Passivation Strategy Toward Stable Photodetector of Epitaxially Connected Quantum Dot Superlattices

Epitaxially connected quantum dot superlattices (Epi-QDSLs) represent a promising platform for high-performance, next-generation photodetectors. Their enhanced electron transport mobility, together with the preservation of quantum confinement, enables efficient charge extraction with high quantum efficiency. This results in high responsivity, detectivity, and faster response time. The ligand-free nature of PbS quantum dots (QDs) in Epi-QDSLs introduces a critical challenge of poor environmental stability, as the conventional surface passivation strategies of ligand exchange are incompatible with ligand-free QDs in the Epi-QDSL system. Here, we examine the air stability of the Epi-QDSL photodetector and investigate the effects of introducing a P(VDF-TrFE) passivation layer on the material properties, device performance, and air stability of Epi-QDSL. The dipole polarization of the dielectric nature of the block copolymer induces an electrostatic n-type doping effect, as confirmed by the field-effect transistor measurement. This doping effect increases electron mobility and facilitates more efficient charge extraction, thereby significantly improving device performance. The hydrophobic nature of P(VDF-TrFE) effectively prevents the progressive infiltration of oxygen and moisture into the PbS QDs, thereby preventing the irreversible degradation suffered by the ligand-free QDs in the Epi-QDSL system.