Building a tetrachromatic photosensor for multi-dimensional information processing

Humans can see only a small sliver of the light spectrum, but some animals have extra cells in their eyes that let them see ultraviolet (UV) light. Bees, for instance, use UV light to seek out nectar-filled flowers, and reindeer use UV light to spot otherwise camouflaged polar bears.

Tetrachromatic vision — the ability to see the three primary colors of visible light plus UV — has the potential to benefit optical sensors in the same way it benefits bees and reindeer. Huang et al. developed an optoelectronic transistor with tetrachromatic sensitivity by using two light-sensitive thin film materials, pentacene and zinc oxide (ZnO).

Their approach allows for simultaneous visible and UV detection along with separate information processing, providing more functionality for a wider range of applications.

“[Previous] works only coupled spatial and spectrum information into static image processing, but did not develop an in-sensor tetrachromatic vision system capable of multi-dimensional information processing functionality,” said author Haifeng Ling.

Their optoelectronic transistor makes use of the visible light sensitivity of pentacene and the UV sensitivity of ZnO. As a result, their transistor exhibits volatile positive photoconductance for visible light and non-volatile negative photoconductance for UV light.

“By independently splitting external information into visible and ultraviolet channels for separate processing, interference between different wavelength is avoided, enabling differential recognition of visible and ultraviolet information and improving the system’s accuracy in handling external information,” said Ling.

In addition to detecting light, the transistor can also perform in-unit processing, recording the motion of stationary visible-light objects and moving UV objects. This data can be combined with a lightweight neural network for object detection and motion tracking.

Source: “Tetrachromatic optoelectronic transistor with multi-dimensional information processing functionality for in-sensor motion perception,” by Wanxin Huang, Yiru Wang, Shanshuo Liu, Jianyu Ming, Yannan Xie, Li Gao, Linghai Xie, and Haifeng Ling, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0303796 .