Improved Performance of Quantum-Dot Photodetectors Using Cheap and Environmentally Friendly Polyethylene Glycol

Abstract

Colloidal quantum dot (CQD) photodetectors (PDs) are developed. The on/off current ratio is improved by applying organic cathode buffer layers (CBLs), such as polyethylenimine ethoxylated (PEIE) and polyethylene glycol (PEG). The on-current of CQD-PDs (QPDs) is increased by the decreased work function of ZnO/CBLs via forming a permanent dipole moment at the interface of ZnO and CBLs. The off-current is significantly decreased by the improved interfacial morphology via softening the ZnO surfaces. In the photoconductive mode for the fast response time of a signal, PEG- and PEIE-treated QPDs exhibit improved photodetecting properties. Notably, the performance of PEG-treated QPDs fluctuates less at the concentration of the prepared CBL solution. The utilization of environmentally friendly and cheap PEG as CBLs is attractive for QPDs. The organic CBL is highly effective for QPDs to improve both on- and off-current characteristics.