Step-like 10-nm channel for high-performance PbS colloidal quantum dots near-infrared photodetector

Abstract

Developing a high-performance photodetector based on PbS colloidal quantum dots (CQDs) always aims to achieve high external quantum efficiency (EQE), responsivity, and temporal response speed. However, reported device structures face challenges in overcoming issues such as surface ligand isolation, high surface trap densities and low charge carrier mobility, which have impeded the electronic coupling of CQDs and significantly limited the performance of the photodetector. To tackle these issues, we have developed a solution by designing step-like devices with a 10-nm channel. This approach utilizes a simple and controllable strategy, incorporating two partially overlapped Au electrodes and an insulating HfO₂ layer. The thickness of the HfO₂ layer provides a means for precise control over the channel dimensions. After the spin-coating process with PbS CQDs, the photodetector exhibits a significantly improved responsivity of 23 A W⁻¹ and an exceptionally high external quantum efficiency (EQE) of 2800% when illuminated with a 1000-nm laser as the excitation source. Furthermore, the photocurrent response time is approximately 100 μs. The exceptional photodetection performance of the PbS CQD-based photodetector can primarily be attributed to its ultra-short channel length, positioning it as an extremely promising alternative for high-performance near-infrared photodetection in the next generation.