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

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ABSTRACT

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.

Significance of the Study:

The findings advance Ge-based solar cell technology by demonstrating the critical role of interfacial engineering in boosting efficiency. The optimized GO/ZnO bilayer offers a low-cost, scalable solution for minimizing recombination losses while maintaining high carrier mobility. This work contributes to next-generation photovoltaics, particularly for tandem and space applications where Ge’s infrared absorption is crucial. The simulation-based approach provides a framework for future experimental validation and industrial adoption of high-performance Ge solar cells.

Summary of the Study:

This study utilized PC1D simulations to optimize the performance of heterojunction-based germanium (Ge) solar cells by engineering interfacial layers. The impact of emitter/base thickness, doping concentrations, and interfacial materials (ZnO, GO, and GO/ZnO bilayer) on photovoltaic parameters was systematically analyzed. Results demonstrated that a 10 nm GO/40 nm ZnO bilayer significantly enhances efficiency (21.15%) by reducing recombination and improving charge transport. The study provides design guidelines for high-efficiency Ge solar cells applicable in space and terrestrial photovoltaics.