Replacing the electron-hole transport layer with doping: SCAPS simulation of lead-free germanium-based perovskite solar cells based on CsGeI3

In recent years, scientists have shown increasing interest in perovskite solar cells because of their remarkable light absorption capabilities and promising prospects, among which germanium-based perovskite solar cells have been praised for non-toxicity. However, the defects between the charge transport layers affect its performance, and the charge transport layer materials also bring environmental hazards due to some organic properties. In this work, we propose to replace the charge transport layer with a solar cell based entirely on the germanium-based perovskite absorption layer by varying the CsGeI3 doping concentration. We created n-CsGeI3 and p-CsGeI3 layers conducive to electron hole transport, thus effectively reducing the defects between the interface transport layers, improving the electron hole transport environment, and improving the transmission efficiency. We employed SCAPS software for designing and optimizing the cell structure, enabling us to model and fine-tune parameters such as band gap, thickness, doping concentration, and defect density. These optimizations led to the calculation of optimal values, resulting in an impressive 34.57 % efficiency. The cell structure developed in this work validates the feasibility of germanium-based perovskite solar cells without electron hole transport layer, reducing environmental risks and optimizing performance parameters to some extent. This provides a valuable reference for future research on such solar cells.