Flexible Large Area SWIR Colloidal Quantum Dot Down Converters Based on Scalable Manufacturing Processes

Abstract The growing demand for efficient, compact, and cost‐effective short‐wave infrared (SWIR) emitters has surged due to their wide‐ranging applications in industries such as biomedical diagnostics, food and pharmaceutical quality control, agriculture, and environmental monitoring. Conventional SWIR sources are limited by bulkiness, inefficiency, and high cost, while phosphor‐converted Light Emitting Diodes (pc‐LEDs) based on transition metal ions or lanthanides face challenges such as fixed wavelengths, narrow absorption bands, and high‐temperature manufacturing processes. Lead sulfide (PbS) colloidal quantum dots (CQDs) offer a promising alternative, combining wavelength tunability, synthesis simplicity, cost‐effectiveness, and high photoluminescence quantum yield (PLQY). In this study, a scalable manufacturing process is introduced to fabricate flexible, high‐performance SWIR down‐converters (DCs) based on PbS CQDs embedded in an ethyl cellulose (EC) polymer matrix. Performance enhancements are achieved through a solution‐phase ligand exchange (SPLE) with 1‐dodecanethiol (DDthiol), improving passivation and device efficiency. When excited by a 980 nm LED, the DC achieves a SWIR output power density of 0.54 mW mm − 2 and a photon conversion efficiency of ≈15%. A practical application is demonstrated with a custom‐built SWIR torch based on thin‐film CQD DCs, shown to penetrate smoke, highlighting the potential of this technology for real‐world use cases.