Investigating the Factors of Increasing the Efficiency of Heterojunction Quantum Dot Solar Cell

Factors affecting on heterojunction quantum dot solar cell’s efficiency includethickness of wide band transparent semiconductor and quantum dot layers, doping level of quantum dots layer and the type of metal used as anode. This paper represents a simulation of a structure consisting of a layer of short ligand coated PbS quantum dots and a layer of ZnO semiconductor and gold anode using COMSOL Multiphysics v5.4 x64. The primary model had 2.62% efficiency for a cell with a Schottky contact between anode and quantum dot layer and 7.95% efficiency for a cell with an ohmic contact. A sweep in doping level of quantum dots layer for 1015, 1016 and 1017 cm-3 led to 7%, 7.95% and 5.2% for ohmic contact and 2.6%, 2.62% and 2.2% for schottky contact, respectively. A sweep in thickness of PbS quantum dot layer from 50nm to 100nm resulted in an advance in cell’s efficiency from 2.1% to 2.91% for a cell with a schottky contact and from 7% to 8.12% for a cell with an ohmic contact, as a conclusion to increasing the depletion region’s length, hence an increase in electric field in the junction area. In addition, ZnO layer’s thickness from 70nm to 150nm showed a decrease in efficiency from 9.4% to 6% due to limitation of exciton’s diffusion length. These excitons are recombined before being harvested by anode and cathode.