Heavy Metal Free Ag₂Se Quantum Dot Inks for Near to Short-Wave Infrared Detection

Infrared (IR) photodetection underpins critical applications, from environmental monitoring to national defense and autonomous navigation. Existing technologies derived from epitaxial HgCdTe and InGaAs are constrained by high cost, complex fabrication, and limited scalability. Colloidal quantum dots (cQD) such as HgTe and PbS have emerged as promising solution-processable alternatives, but their reliance on toxic heavy metals impedes broad adoption under increasingly stringent regulatory frameworks. Here, we report high-performance, heavy-metal-free Ag₂Se cQD photodetectors utilizing a solution phase ligand exchange (SPLE), which produces reproducible devices through a single-step deposition, eliminating the need for multistep layer-by-layer depositions used in conventional solid-state ligand exchange approaches. The SPLE-based photoconductors exhibit responsivities of ∼150 mA/W under a 0.3 V bias in the 800-1250 nm range. We also demonstrate a self-powered photodiode achieving a specific detectivity of 6.5 × 10¹⁰ Jones at 1200 nm, with a 3 dB bandwidth of 18 kHz and sub-50 μs response times, rivaling those of other heavy-metal-free cQDs. This work positions Ag₂Se cQDs as a viable, regulatory compliant alternative for near- to short-wave IR detection and offers a strategy for improving performance in larger Ag₂Se cQDs active in the midwave IR regime.