| 초록 |
Near-infrared (NIR) photodetectors, which sense photons with wavelength longer than 750 nm, have attracted much attention in various fields such as non-invasive imaging sensors, optical communications, environmental monitoring and night vision systems. To date, the conventional NIR photodetectors based on crystalline silicon need to form a photoactive layer with sufficiently thick junctions (t ＞ 200 μm) to maximize the number of absorbed NIR photons as well as enhance the device performance, which limits device miniaturization capability in the integrated circuit and further application. Recently, Cu(In, Ga)(S, Se)2 (CIGS) films have emerged as an alternative material due to their ability to optimize bandgap profile by adjusting the composition distribution, high photon-to-charge conversion efficiency, and superior environmental stability. This is beneficial to highly stable NIR photodetector applications. In this presentation, solution-processed NIR photodetectors operating at 980 nm based on a potassium (K)-incorporated CIGS photoactive layer are introduced. Through K-incorporation in the bulk CIGS films contributing to promote Se penetration, a bandgap grading structure and chalcopyrite crystallization were induced, resulting in efficient charge carrier separation and transport in the device. In this regard, the effect of K-incorporation was proved by investigating an atomic concentration profile, chalcopyrite morphology, and Hall mobility, comparing to unmodified CIGS films. Based on this, we demonstrated the K-incorporated CIGS NIR photodetectors with improved photoresponse characteristics at NIR 980 nm under the reverse bias condition. Finally, we suggest a possible mechanism for the external quantum efficiency exceeding 100% at low light power, which is relevant to the photoconductive gain effect. |
