Enhanced and Passivated Co-doping Effect of Organic Molecule and Bromine on Graphene/HfO₂/Silicon Metal-Insulator-Semiconductor (MIS) Schottky Junction Solar Cells

Graphene (Gr) has shown a significant role in photovoltaic applications due to its exclusive properties. In this study, we established a facile approach to fabricate p-Gr/HfO₂/n-silicon, a metal-insulator-semiconductor (MIS) Schottky junction solar cell. Nevertheless, the poor work function of Gr and high-density defect states at the Gr/Si interface obstruct the efficiency of solar cells. To avoid this problem, the optimal thickness of the interfacial layer (HfO₂) is employed, which circumvents the recombination process at the Gr/Si interface. Additionally, to boost the Schottky barrier height and Gr's work function, a combination of p-type co-doping of organic molecule 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) and Br is studied. Therefore, a higher work function aims to encourage the built-in potential, which ultimately improves the open-circuit voltage and current density and deteriorates the series resistance of solar cells. Hence, a unique combination of dopants resulted in improved efficiency of up to 12.31%. Moreover, devices with double layer (MoO₃/HfO₂) passivation have been enabled to provide outstanding stability for over 180 days. The combined effect of p-type co-doping and double layer passivation developed a solar cell having a significant efficiency of 14.01%. Thus, this work intends to show a promising, high-performance and stable MIS Schottky junction solar cell for massive commercialization of photovoltaic devices.