p-type NiO_x ultrathin film as highly efficient hole extraction layer in n-type PbS quantum dots based NIR photodiode

Recently, the development of zero-dimensional (0D) materials has experienced significant growth. Among them, PbS colloidal quantum dots (CQDs) have received special attention due to their outstanding properties, including tunable optical absorption ranging from 600 to 2600 nm (size dependent bandgap) and easy solution synthesis. PbS CQDs are considered as one of the most promising materials for the next generation of infrared sensors. Hence, there is a growing interest in their use in industrial spheres. One of the major keys to obtaining highperformance devices is the realization of efficient charge extraction contacts on PbS CQDs films. In this work, we have demonstrated an efficient hole extraction layer (HEL) using NiOx ultra-thin film on infrared p-i-n photodiode based on only n-type PbS nanocrystals (CQDs). We compared the performance with the standard optimized MoOx. We obtained a significant gain in external quantum efficiency (EQE), a decrease of the operating bias, while keeping the same dark current level.