Dual passivation enables high-performance PbSe quantum dot short-wave infrared photodetectors

Short-wave infrared (SWIR) photodetectors based on colloidal quantum dots (CQDs) hold great promise for their size-tunable bandgaps and low-cost solution processability. PbSe CQDs, in particular, offer distinct advantages for SWIR optoelectronic applications. However, surface trap states and electronic inhomogeneity still limit their device performance. Here, we present a dual-passivation (DP) strategy that synergistically combines lead halide with 2-mercaptoethanol (ME) to effectively passivate PbSe CQD surfaces. This method simultaneously removes long-chain insulating ligands and forms robust Pb–S bonds, resulting in significantly reduced trap states, enhanced carrier lifetime, and improved structural and electronic uniformity. Based on the DP PbSe CQDs, short-wave infrared photodetectors enable a low dark current density of 2.51 × 10⁻⁷ A cm⁻² at -0.5 V, high responsivity of 0.527 A/W, and an external quantum efficiency of 50.2%. The specific detectivity (D*) of 1.51 × 10¹² Jones Jones—over four times higher than control devices. This dual-passivation strategy offers a new route for building high-performance PbSe CQD devices.