Upconversion photodetectors convert photons from the infrared to the visible light spectrum and are of use in applications such as infrared detection and imaging. High-performance upconversion devices are, however, typically based on vacuum-deposited materials, which are expensive and require high operating voltages, which limits their implementation in flexible systems. Here we report solution-processed optical upconversion photodetectors with a high photon-to-photon conversion efficiency of 6.5% and a low turn-on voltage of 2.5 V. Our devices consist of a colloidal lead sulfide quantum dot layer for harvesting infrared light that is monolithically coupled to a cadmium selenide/zinc selenide quantum dot layer for visible-light emission. We optimized the charge-extraction layers in these devices by incorporating silver nanoparticles into the electron transport layers to enable carrier tunnelling. Our photodetectors exhibit a low dark current, high detectivity (6.4 × 10¹² Jones) and millisecond response time, and are compatible with flexible substrates. We also show that the devices can be used for in vitro bioimaging.

上转换光电检测器将光子从红外转换为可见光谱，并在诸如红外检测和成像等应用中使用。但是，高性能上变频设备通常基于真空沉积的材料，这种材料昂贵且需要高工作电压，这限制了它们在灵活系统中的实现。在这里，我们报告经过溶液处理的光学上转换光电探测器，其光子到光子的转换效率高，为6.5％，开启电压低，为2.5V。我们的设备由胶体硫化铅量子点层组成，用于收集红外光，单片耦合至硒化镉/硒化锌量子点层，用于可见光发射。通过将银纳米颗粒结合到电子传输层中以实现载流子隧穿，我们优化了这些器件中的电荷提取层。我们的光电探测器表现出低的暗电流，高的探测灵敏度（6.4×10¹² 毫秒）和毫秒响应时间，并且与柔性基板兼容。我们还显示该设备可用于体外生物成像。