Thermal Spin Coated PbS QD SWIR Imager for Non-Invasive Glucose Monitoring

Colloidal lead sulfide quantum dots are attractive for short-wave infrared photodetectors due to their tunable bandgap and solution-process compatibility, yet device performance is often limited by high dark current, inefficient carrier extraction, and poor stability. Here, we report a new strategy of combining thermal spin-coating and annealing that improves quantum dot film quality by regulating solvent evaporation kinetics and stacking behavior during deposition. Elevating the substrate temperature during spin-coating induces dense and uniform quantum dot assemblies with reduced trap density and improved interfacial contact. Photodetectors fabricated at an optimized temperature of 65°C exhibit substantially enhanced performance, including a responsivity of 0.765 A/W, a specific detectivity of 3.57 × 10^{1 1} Jones, and a -3 dB bandwidth of 108 kHz, accompanied by over 50% reduction in dark current density. Importantly, the optimized devices show improved long-term stability, retaining lower dark current and higher external quantum efficiency after prolonged storage without encapsulation. Leveraging these advantages, the photodetectors are further integrated into an imaging array and applied to non-invasive glucose monitoring using dual-wavelength ratiometric detection. This work establishes thermal spin-coating as a simple and scalable route toward high-performance, stable quantum dot infrared photodetectors for imaging and biomedical sensing applications.