Highly Efficient Top-Emitting Infrared-to-Visible Up-Conversion Device Enabled by Microcavity Effect

Infrared (IR)-to-visible up-conversion device allows a low-cost, pixel-free IR imaging over the conventional expensive compound semiconductor-based IR image sensors. However, the external quantum efficiency has been low due to the integration of an IR photodetector and a light-emitting diode (LED). Herein, by inducing a strong micro-cavity effect, a highly efficient top-emitting IR-to-visible up-conversion device is demonstrated where PbS quantum dots IR-absorbing layer is integrated with a phosphorescent organic LED. By optimizing the optical cavity length between indium tin oxide (ITO)/thin Ag/ITO anode and semi-transparent Mg:Ag top cathode, the up-conversion device yields 15.7% of photon-to-photon conversion efficiency from the top-emission. The high efficiency can be achieved under a low IR transmission through the semi-reflective anode. Finally, pixel-free IR imaging is demonstrated using the up-conversion device, boosting the effect of micro-cavity on the brightness and the contrast of an IR image.