Interface Engineering for High Photoresponse in PbS Quantum-Dot Short-Wavelength Infrared Photodiodes

A simple and effective strategy, that is the use of 2-Methoxyethanol rather than anhydrous ethanol as the ZnO precursor solvent, is developed to greatly improve the photoresponsivity in the PbS colloidal quantum dot (CQD)/ZnO heterojunction short-wavelength infrared (SWIR) photodiodes. This approach significantly modifies the PbS/ZnO interface through an increase of electron concentration and a reduction of surface defects in the ZnO layer, which is critical to suppressing carrier recombination at the PbS/ZnO interface. The optimized photodiodes show superior figures of merit, including low dark current density of 1.28× \,\,10^-8A/cm2at −0.5 V, high photoresponsivity of 0.47 A/W and high specific detectivity of 2.22× \,\,10^12Jones at 1413 nm, and fast response/recovery time of 6.8/8.6μ s.