Colorful visualization detection of near-infrared light enabled by an upconversion device with a color-tunable quantum dot light-emitting unit

Color-tunable near-infrared (NIR)-to-visible upconversion devices (UCDs) that correlate the NIR power intensity with the visible emission color are highly desired and hold promise for interactive signal visualization in intelligent optoelectronic devices. In this work, solution-processed color-tunable UCDs integrating a NIR sensing photodetector unit and a color-tunable quantum dot (QD) light-emitting unit are demonstrated. We mixed the red and green QDs in a single emissive layer (EML) for multi-color emission from the UCDs, which is quite different from the previously reported work that used multiple EMLs with different colors. The image color of the resulting color-tunable UCDs can be modulated by bias voltage and driving current and shows a wide color-span range from red to green as the NIR intensity increases. Finally, we present a qualitative correlation between the incident NIR power intensity and the visible emission color, which enables colorful visualization detection of NIR light.