en.Wedoany.com Reported - A research team at Nagoya University has developed gallium-doped zinc oxide nanosheets that enable a single pixel to simultaneously detect red, green, and blue light. This material is expected to be used in compact devices such as smartphones and medical endoscopes to improve camera resolution.
Unlike conventional sensors, these nanosheets allow a single pixel to detect the intensity of red, green, and blue light while remaining nearly transparent. The material is ultra-thin, lightweight, and can withstand temperatures up to 400 degrees Celsius, making it suitable for extreme environments such as space hardware and automotive systems. The research findings were published in the journal ACS Nano.
Most commercial cameras use a Bayer array, arranging red, green, and blue color filters in a checkerboard pattern over pixels. Since each pixel perceives only one color, full-color images must be reconstructed from neighboring pixels. If a single pixel can detect all three colors, the total number of pixels can be reduced by up to 75%, thereby shrinking the sensor while maintaining image resolution. Transparent nanosheets are well-suited for this approach because they allow light to pass through and can be vertically stacked in multiple layers, with each layer detecting a different color. This sensor also eliminates the complex semiconductor processes required for traditional RGB sensors, simplifying production and reducing costs.
The research team, led by Professor Minoru Osada at the Institute of Materials and Systems for Sustainability, Nagoya University, along with Ruben Canton-Vitoria and Vivid Meelab, focused on zinc oxide nanosheets, which are highly transparent and chemically stable. However, initial experiments showed that these nanosheets had a weak response to visible light, limiting their application in camera sensors. To address this limitation, the team tailored the electronic structure of zinc oxide by adding gallium, creating trap states that capture electrons and convert light into electrical signals. This improvement enabled the nanosheets to respond strongly to visible light while maintaining transparency.
Analysis revealed that the gallium-doped zinc oxide nanosheets converted only 0.005% of absorbed light energy into photocurrent, while transmitting 99.995% of visible light per layer. Despite the extremely low energy utilization, the improved nanosheets achieved a sensitivity of 800 amperes per watt, far exceeding the typical 10 amperes per watt of commercial sensors. The trap states allow a strong response to the small amount of absorbed light, while most light is transmitted to subsequent layers. This property enables color-selective stacking. The team developed an ultra-thin sensor: the first layer of gallium-doped zinc oxide uses photoactive trap states to detect the entire visible spectrum; after filtering out red light, the second layer detects green and blue light components; finally, through a green cut-off filter, the last layer detects blue light alone. Experiments confirmed that the device successfully reproduced full-color images with half the error of conventional cameras. Minoru Osada stated that this optical sensor closely mimics how the human eye distinguishes red, green, and blue colors, with the brain reconstructing colors by combining responses from three types of visual cells.
In addition to optical performance, the device maintained stable photoresponse at temperatures up to 400 degrees Celsius in air, with consistent performance under vacuum and humid conditions. The sensor can also be fabricated using a room-temperature solution process, eliminating the need for high-temperature treatments and complex microfabrication required by traditional sensors. By integrating multiple light detection functions into a single device, the team has demonstrated a path toward smaller, more integrated, and higher-performance optoelectronic devices than existing cameras, at a lower cost.
