Theoretical insights into Z-scheme BAs/GeC van der Waals heterostructure for high-efficiency solar cell†

The urgent need for solar electricity production is critical for ensuring energy security and mitigating climate change. Achieving the optimal optical bandgap and effective carrier separation, essential for high-efficiency solar cells, remains a significant challenge when utilizing a single material. In this study, we design a BAs/GeC heterostructure using density functional theory. Our findings indicate that the BAs/GeC heterostructure exhibits direct bandgap semiconductor characteristics. Notably, the BAs/GeC heterostructure demonstrates excellent optical absorption within the infrared and visible light spectrum. Moreover, significant carrier spatial separation was suggested, facilitated by a Z-scheme pathway. Furthermore, applying biaxial strains revealed that the BAs/GeC heterostructure is unstable under compressive strain. However, the electronic and optical properties can be tuned using tensile biaxial strains. The calculated power conversion efficiency (PCE) of the BAs/GeC heterostructure is approximately 31%, as determined by the Scharber method. Hence, the combination of an appropriate bandgap, substantial carrier separation, and superior photoelectric conversion efficiency positions the BAs/GeC heterostructure as a promising candidate for high-efficiency solar cells.