Quad‐Band Short‐Wave Infrared Detection Using Bandgap‐Controlled Ag₂Te Quantum Dots

Multispectral photodetection in the short‐wave infrared (SWIR) range has been highly desirable for applications such as night vision, quality inspection, and bio‐imaging. Colloidal quantum dots (QDs) have been extensively explored as a promising alternative to conventional epitaxial semiconductors for multispectral photodetection owing to their size‐tunable bandgap‐controlled optoelectronic properties and potential for low‐cost, high‐throughput fabrication. Here, a multispectral SWIR photodetector is demonstrated based on four distinct sizes of heavy‐metal‐free Ag 2 Te QDs, each patterned side‐by‐side using a direct QD photopatterning process‐ involving QD film deposition, ultraviolet‐induced selective QD ligand crosslinking, and pattern development. This enables precise spatial integration of the four different QD channels into a single device platform that is independently addressible, allowing integrated multispectral SWIR detection within a monolithic platform. The resulting multispectral Ag 2 Te QD channels show maximum responsivities of 188.4, 173.5, 155.6, and 185.8 mA W −1 at 1150, 1350, 1550, and 1800 nm, respectively. By leveraging the distinct photoresponses of four spectrally differentiated Ag 2 Te QD channels to SWIR input light, it is demonstrated that the multispectral photodetector enables simple, non‐spectrometric wavelength identification—highlighting a unique capability unattainable with conventional single‐size‐QD devices.