Performance Optimization of Lead-Free RbGeI ₃ Perovskite Solar Cells with rGO and Graphene Interfaces

Perovskite solar cells (PSCs) are new promising candidates for future energy solutions due to recent developments in photovoltaic technology. However, many perovskite materials include lead, which limits their practical application and presents health and environment issues. The potential for lead-free PSCs using Rubidium based germanium iodide (RbGeI ₃ ) as the absorber layer is examined in this work. The numerical analysis using SCAPS-1D showcases the advantage of employing rGO as a front contact in perovskite solar cells, since its tunable work function allows enhanced device performance. The proposed device output metrics obtained are power conversion efficiency, eta of 32.1%, open circuit voltage, V _OC of 1.11 V, short circuit current density, J _SC 32.37 mA cm ⁻² and fill factor, FF of 89.15%, which advances the study related to the performance parameters of perovskite solar cells. The results prove that higher sheet resistance in the rGO electrode leads to substantial ohmic losses degrading device efficiency. Hence, obtaining low sheet resistance in rGO films is crucial for maximizing the performance of perovskite solar cells. Furthermore, the impact of graphene as an intermediate layer between perovskite and HTL is presented. It operates as a passivation layer. The effect of temperature and optical transmittance changes are also investigated.