Design and optimization of the performance of PbS quantum dot based vertical photodetector

Abstract

Quantum dots (QDS) are widely used as photoactive materials for various optoelectronic applications, such as light-emitting diodes, photodetectors, lasers, and solar cells, because of their unique and outstanding physical properties for fabricating devices via solution-processing techniques and for varying the sizes of QD to modulate the band gap. In this study, we constructed a numerical model of a vertical photodetector using lead sulfide (PbS) quantum dot layer undergoing ligand exchange treatment with tetrabutylammonium iodide (TBAI) as the light absorption layer to obtain an optimized high-performance photodetector using 1D-Solar Cell Capacitance Simulator (SCAPS) software. For the hole transport layer (HTL) and electron transport layer (ETL), a PbS quantum dot layer that employs an ethanedithiol (EDT) ligand exchange scheme and a zinc oxide (ZnO) layer were utilized, respectively, with gold (Au) and indium tin oxide (ITO) as the bottom and upper electrodes, respectively. After optimizing the thickness and doping concentration of the absorption layer, we obtained a maximum responsivity of 0.4675 A/W and detectivity of 2.44×1013 Jones at a reverse bias of 0.5 volts after optimizing of thickness and doping concentration of absorption layer showing an improvement of 19% and 87.7% respectively compared to the initial structure whose parameters originated from studies of PbS quantum dot solar cells with the same structure and materials, although optimization of other transport layers do not provide as great performance enhancement as absorption layer. This study demonstrates that the structural parameters of solar cells are not always applicable to photodetectors, and that photodetectors have great potential for numerical optimization.