Band-engineered dual-band visible and short-wave infrared photodetector with metal chalcogenide colloidal quantum dots

Dual-band photodetectors have attracted significant attention because of their potential in optical communication, biochemical detection, and environmental monitoring. Colloidal quantum dots (CQDs) are promising materials for dual-band photodetectors because of their size-tunable bandgaps with wide spectral tunability and easy solution processability. Here, we propose a dual-band visible (VIS) and short-wave infrared (SWIR) detector based on metal chalcogenide CQDs (HgTe and CdTe CQDs). An n-type ZnO layer between the CdTe and HgTe layers is introduced as a hole-blocking layer to prevent hole injection from the different sensing layers, enabling the detector to switch between the VIS and SWIR modes by changing the polarity and magnitude of the bias voltage. The device exhibits an excellent performance with high responsivities of 0.5 and 1.1 A W⁻¹ for the two bands that peak at 700 and 2100 nm, respectively. The detectivity of the device can reach 1.1 × 10¹¹ Jones at +3 V (VIS) and 4.5 × 10¹¹ Jones at −2 V (SWIR). In addition, VIS/SWIR dual-band imaging is realized, which provides more comprehensive object information than single-band detectors.