Improved Infrared Photoresponse Through Coupling of Lead Sulfide Colloidal Quantum Dots and Amorphous Selenium

Infrared photodetectors are playing an increasingly important role in our modern society, and the use of colloidal quantum dot active layers have reduced the complexity at which these detectors can be fabricated and tuned. However, a compromise between maximizing charge transfer and absorbance is often necessary to optimize detector performance. Amorphous selenium (a-Se) is known for its uniform properties and ease of deposition scalable to a large area, as well as its ability to provide avalanche gain via hole impact ionization at high applied electric fields. In this work, we combine an a-Se hole transport layer with a lead sulfide (PbS) colloidal quantum dot active layer in order to decouple charge transport and absorption, and we show that this is beneficial for the infrared photoresponse. Although more work remains to improve device performance and stability, preliminary specific detectivity of 2.5 x 10¹¹ Jones at 980 nm and 3dB frequency of 2.5 MHz demonstrate that this technology has the potential to compete with and surpass the current state of the art.