High Performance Infrared InAs Colloidal Quantum Dot Photodetector with 79% EQE Enabled by an Extended Absorber Layer

Colloidal quantum dots (CQDs) with tunable bandgaps in the NIR‐SWIR range are highly valued for infrared applications including LiDAR, interactive displays, and biometrics. Particularly, for environmental considerations, photodetectors (PDs) using InAs CQDs are actively being explored. However, their performance still lags behind that of Pb‐based devices. Herein, an effective strategy to improve the photodetection characteristics of InAs CQD PDs by enhancing the incident photon usage is presented. By engineering the solvent of InAs CQD ink to increase volatility, the controllable range of absorber layer thickness is substantially extended. Then, the thickness‐ and bias‐dependent performance of InAs CQD PDs are systematically studied, guided by optical simulations. Under optimal conditions, an external quantum efficiency (EQE) of 79%, a responsivity of 0.6 AW −1 –the highest reported for InAs CQD photodiodes, and a detectivity of 3.1 × 10 11 Jones at 940 nm are achieved. Furthermore, it is found that increasing the absorber layer thickness reduces device capacitance, resulting in a faster response time of 46 ns. This study provides optical and electrical insights into how absorber layer thickness affects InAs CQD PD performance and outlines design principles for high‐performance optoelectronic devices with specified light‐absorbing layers, paving the way for the development of advanced optoelectronic devices.