Enhancing Perovskite Solar Cells Performance Through Investigation of Ruddlesden–Popper (2D) Cs2GeI2Br2 and (3D) CsGeI2Br Absorbers

Ruddlesden–Popper (RP) perovskite materials are gaining traction in optoelectronic applications due to their unique structure and adjustable properties. This study investigates the potential of RP (2D) Cs₂GeI₂Br₂ and (3D) CsGeI₂Br absorbers in enhancing perovskite solar cell (PSC) performance. Through rigorous analysis, we find that integrating RP phases improves charge transport and reduces defects, leading to superior device performance. The results showed a direct bandgap (1.45 eV for 2D), high optical absorption (above 50 × 10⁴ cm^–1 for 3D), low reflectivity, and energy loss, indicating solar cell suitability. The calculated effective mass values (m_e^*, m_h^*) (0.245, 0.423 eV) for Cs₂GeI₂Br₂ closely resemble those reported for Cs₂PbI₂Br₂ and Cs₂PbI₂Cl₂, indicating similar charge carrier behavior in these materials. Our research provides valuable insights for optimizing PSCs with alternative structures. Additionally, simulations explore various hole transport layers and temperature effects on key electrical parameters under standard AM 1.5 G solar radiation using the SCAPS-1D software, achieving a maximum efficiency of approximately 29.59% for the PSC prototype at an ambient temperature of 25 °C.