Japanese team develops Pb-free QDs for NIR and SWIR sensing
In joint research with the Torimoto Laboratory at Nagoya University, Tanaka, a Japanese industrial precious metals company, has developed a lead-free quantum dot material made of Ag-S-Te that is responsive to near-infrared light.
The material will be presented at Okinawa Colloids 2026, an international conference to be held in Okinawa from November 1 to 6, 2026, and at nano tech 2026, the 26th International Nanotechnology Exhibition & Conference, to be held from December 16 to 18, 2026.
Infrared sensing technologies are being applied in a wide range of applications including 3D sensing and wearable devices, facial recognition on smartphones, industrial inspection cameras, automotive LiDAR, and biosensing.
For these applications, InGaAs has conventionally been used as the primary photodetector material. Although it can detect infrared light at wavelengths of up to 1,700 nm with high sensitivity, the manufacturing process is complex, involving the use of vacuum processes, and yield and cost during mass production remain challenges.
Demand for indium, meanwhile, has recently been growing rapidly in cutting-edge fields such as next-generation high-speed communication semiconductors for AI data centres, perovskite solar cells, and smartphone displays.
PbS QD materials are a low cost alternative to conventional InGaAs becuase they can produced using printing processes. However, they contain lead, which is regulated under the RoHS Directive.
Tanaka and Nagoya University's Ag-S-Te compound semiconductor quantum dot material requires no vacuum process and can be deposited using printing processes suitable for large-area production.
In performance evaluations conducted by Tanaka, the newly developed Ag-S-Te quantum dots were incorporated as the photodetection layer in a simple photosensor, which achieved a maximum external quantum efficiency (EQE) of 18.4 percent for short-wave infrared (SWIR) light in the 1,200–1,700 nm wavelength range. This wavelength range is less susceptible to noise from sunlight and the effects of adverse weather, enabling high-precision sensing outdoors. Light in this wavelength range also offers greater eye safety and readily penetrates materials and biological tissue.
This development is expected to enable practical applications across a wide range of fields where the adoption of high-performance infrared sensors has previously been limited by cost and lead restrictions. These include consumer electronics such as smartphones (3D sensing for facial recognition and other functions), automotive LiDAR, industrial inspection cameras, and biosensing.
