Suppression of the dark current in PbS quantum dot infrared photodetectors through the introduction of a CuInSeS interfacial layer

Abstract

Lead sulfide (PbS) colloidal quantum dot (CQD) materials are extensively utilized in the fabrication of near-infrared detectors. Advanced PbS quantum dot infrared detectors often employ ligand exchange processes to enhance the performance of the active layer. This process involves the replacement of long-chain ligands, which exhibit poor conductivity, with short-chain ligands, such as 1,2-ethanedithiol (EDT) in the treatment of PbS. However, conventional solid-state ligand exchange techniques are prone to cause inherent cracking, resulting in significant leakage currents that limit detector sensitivity. To address this challenge, we introduce a copper indium selenium sulfur (CuInSeS) quantum dot interfacial layer, resulting in the creation of a smooth and crack-free film. This method effectively optimizes the interfacial contact between PbS and ZnO. Additionally, this layer concurrently establishes a gradient energy level, facilitating the transport of charge carriers. This results in a decrease in the dark current to 4.6 × 10⁻⁸ mA under a −1 V bias, achieving a detectivity of 1.87 × 10¹² Jones. The results demonstrate that the quantum dot interfacial layer effectively suppresses the dark current of the detector, addressing the deficiencies associated with the solid-state ligand exchange technique. This work provides a direction for further research on detectors.