An investigation and simulation of the graphene performance in dye-sensitized solar cell

Recently, dye-sensitized solar cells (DSSCs) have become the center of attention due to low manufacturing cost. While dye-sensitized solar cells are cheap, they have relatively low efficiency. Therefore, their industrialization process hasn't been completed yet. In this study, physical and electrical characteristics of graphene, as part of a semiconductor used in DSSCs is analyzed. A proper model to simulate the process in silvaco software is proposed and implemented. In the current DSSC, indium tin oxide, platinium and poly phenylene vinylene (PPV) are employed as the transparent conductive oxide, counter electrode and electrolyte, respectively. To improve the performance of solar cell, in the electrolyte part, the characteristics of the poly(3-hexylthiophene), was attributed to the PPV. The positioning of substances is done according to their energy gap and the studies are carried out in fixed temperature and standard thicknesses. It is quite evident that the TiO2-graphene composite has better efficiency compared to the TiO2-ZnO composite, due to the high mobility of graphene. Thus, the recombination of excited electrons and holes in the highest occupied molecular orbital band significantly decreases in the TiO2-graphene composite in comparison with the TiO2-ZnO composite. This results in an increment in the Fermi level and consequently the open circuit voltage, leading to the increased efficiency of the solar cell. An efficiency equal to 9.3% is achieved in case of graphene-TiO2, while in ZnO-TiO2 composite, only 6.5% is obtained.