Simulation–Based Optimization of Graphene Oxide Interfacial Layers in Heterojunction Germanium Solar Cells Using PC1D

Heterojunction-based solar cells employing germanium (Ge) as the absorber material have gained considerable attention due to their promising optoelectronic properties, high efficiency potential, and compatibility with cost-effective fabrication techniques. However, critical challenges such as interfacial recombination losses and optical inefficiencies continue to limit their performance. This study utilizes PC1D simulations to systematically investigate the role of an optimized graphene oxide (GO) interfacial layer in improving the photovoltaic performance of Ge-based heterojunction solar cells. The incorporation of GO and zinc oxide (ZnO) as interfacial and antireflection layers was applied to analyze their impact on key photovoltaic parameters, including Voc, Jsc, FF, and overall PCE. This study demonstrates that the integration of an efficient GO interfacial layer significantly reduces recombination losses at the heterojunction interface while enhancing charge carrier extraction. Furthermore, ZnO as an antireflective coating (ARC) in Ge-based heterojunction minimizes optical losses, leading to improved light absorption and current generation. The optimized Ge-based heterojunction device with GO/ZnO layer attains the highest PCE of 17.4% with Isc=0.0495A, Voc=0.4208V, Pmax=0.0174W and FF=83.53%. As compared to conventional Ge-based devices, a notable enhancement in device efficiency is recorded via the parametric optimization of interfacial layer thickness, ZnO ARC layer thickness and doping concentrations. The findings highlight the critical influence of interfacial engineering in maximizing the performance of Ge-based photovoltaic devices. This study provides valuable insights for the design and fabrication of high-efficiency heterojunction solar cells, paving the way for their practical implementation in next-generation photovoltaic technologies.