Researchers in Spain have developed a new method for synthesizing colloidal quantum dots from nontoxic silver telluride. This breakthrough could pave the way for cheaper and more compact photodetectors capable of detecting shortwave infrared (SWIR) light. SWIR light has various applications in sensing and imaging, including self-driving cars, environmental monitoring, passive night vision, and biomolecular imaging.
Current SWIR detectors are expensive and difficult to integrate with existing electronics. The use of colloidal quantum dots, however, could significantly reduce manufacturing costs and be compatible with complementary metal-oxide-semiconductor (CMOS) technology. The challenge has been finding environmentally friendly nanocrystals that can absorb radiation at the necessary wavelengths. Most nanocrystals used in quantum dots contain toxic heavy metals such as lead and mercury.
The team of researchers at the Institute of Photonic Sciences in Barcelona has now solved this problem by creating nanocrystals of silver telluride. By tuning the size of these nanocrystals, they were able to control the range of infrared radiation they absorb. The researchers identified new precursors that decompose and nucleate into nanocrystals of specific sizes. They were able to create spherical nanocrystals with diameters ranging from 3 to 7 µm, with each size corresponding to a specific absorption peak.
The researchers then used these quantum dots to create a SWIR photodetector. The detector demonstrated high sensitivity and a linear response across a broad range of input powers. The team also integrated the photodetector with a readout integrated circuit to create a proof-of-concept image sensor. When compared to a standard silicon-based camera, the new device was able to reveal hidden details in photographs illuminated with SWIR light.
Despite these promising results, the researchers acknowledge that further improvements are needed before commercialization. They are focused on increasing the efficiency of the device and reducing dark currents. With continued research and development, these quantum dots could revolutionize the field of photodetection and open up new possibilities for SWIR imaging and sensing applications.