High-Performance Photodiodes Based on In-Situ Etched\nPbSe Colloidal Quantum Dots with Responses Extended to 2500 nm

The\nperformance of PbSe colloidal quantum dot (CQD) based photodiodes\nwith responses beyond 2000 nm was far from satisfactory and has rarely\nbeen reported. The difficulty in obtaining chemically stable large-sized\nPbSe CQDs was the main reason. In this work, chloride ions in weak\nacidic solvent were introduced to in-situ etch out the Se atoms on\nthe surfaces of PbSe CQDs and formed a −Pb–Cl protection\nlayer. As a result, there were no longer any easily oxidized Se atoms\nexposed to the ambient environment. The mechanism behind our method\nfor stabilizing PbSe CQDs was distinct from the commonly reported\nones such as attaching new adlayers directly. The photodiodes with\nthe etched PbSe CQDs achieved 0.75 A/W responsivity at λ = 2200\nnm, 0.15 V open circuit voltage and 100% internal quantum efficiency\nwithout the assist of photoconductive gains, which were the best records\nfor PbSe-based photodiodes working beyond 2000 nm.