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

The performance of PbSe colloidal quantum dot (CQD) based photodiodes with responses beyond 2000 nm was far from satisfactory and has rarely been reported. The difficulty in obtaining chemically stable large-sized PbSe CQDs was the main reason. In this work, chloride ions in weak acidic solvent were introduced to in-situ etch out the Se atoms on the surfaces of PbSe CQDs and formed a −Pb–Cl protection layer. As a result, there were no longer any easily oxidized Se atoms exposed to the ambient environment. The mechanism behind our method for stabilizing PbSe CQDs was distinct from the commonly reported ones such as attaching new adlayers directly. The photodiodes with the etched PbSe CQDs achieved 0.75 A/W responsivity at λ = 2200 nm, 0.15 V open circuit voltage and 100% internal quantum efficiency without the assist of photoconductive gains, which were the best records for PbSe-based photodiodes working beyond 2000 nm.