To improve device performance of self-driven heterojunction photodetectors by inserting a thin layer of silver nanoparticles into the electron-transporting layer

Lead selenide colloidal quantum dots (CQDs) are widely used in infrared photodetectors due to their size-dependent bandgap tunability, facile solution-processing techniques and low cost. Heterojunctions (HJs) are usually used to construct device to facilitate the separation of excitons and the transportation of photogenerated carriers. Based on the solution-processed HJ photodetector ITO/ZnO/PbSe/Ag, in which PbSe CQDs layer acts as the active layer and ZnO nanoparticles (NPs) layer as the electron-transporting layer, a greatly enhanced-performance was obtained after inserting 10 nm Ag NPs layer within the ZnO NPs layer close to the HJ ZnO/PbSe interface. By optimizing the concentration of Ag NPs solutions and the location of Ag NPs thin layer in ZnO film, the maximum responsivity of the self-driven HJ photodetector ITO/ZnO(50 nm):Ag-NPs(10 nm):ZnO(50 nm)/PbSe(300 nm)/Ag reaches to 6.25 mA/W with a specific detectivity D* of 5.17 ×10¹¹ Jones under 8.5 μW/cm² 1550 nm illumination at zero bias. Further, the underlain physical mechanisms for the enhanced-performance were discussed in details. In this way, it provides a very efficient method for enhanced-performance self-driven HJ photodetectors by inserting a thin layer of metal NPs into the electron-transporting layer close to the heterojunction interface.