Near-infrared (NIR)-to-visible optical upconversion devices which convert incident NIR light to output visible light have been studied with great interest since they can be used in various fields such as low-cost pixelless NIR imaging, night vision, production monitoring, and biomedical imaging. Currently, the commercially available NIR sensor is based on an epitaxially grown III-V compound semiconductors, and integrated on a siliconbased readout circuit, so it involves complicated manufacturing process and high cost. NIR-to-visible optical upconversion devices can be manufactured by integrating a photodiode (PD) and a light-emitting diode (LED).
These devices emit visible light from the LED by charge carriers generated by the NIR light when it is absorbed by PD. As a result, they convert the NIR light into the visible light.
In this study, NIR-to-visible optical upconversion device was fabricated by integrating organic PD (OPD) and quantum-dot LED (QLED). Since it has multilayer structure and most of the processes are carried out as a solution process, an orthogonality in solution process is particularly important. We successfully confirmed the operation of the NIR-to-visible optical upconversion device by illuminating the NIR light to device. When there was no NIR light, it didn’t work. However, when NIR light was illuminated, photogenerated charge carriers promoted the injection of holes into the quantum-dot layer, which resulted in low operational voltage and higher luminance. Moreover, this device emitted visible light at a specific position where NIR light was illuminated, allowing pixelless NIR imaging without any complicated pixel fabrication process.