Device Modeling and Performance Enhancement of Ecologically Viable CsGeI ₃ ‐Based Perovskite Solar Cells: A Detailed Investigation of Charge Transport Layer Technology

ABSTRACT The development process of environmentally friendly and sustainable perovskite solar cells (PSCs) necessitates substitutes for harmful lead (Pb) and unstable tin (Sn) based absorber materials. Germanium (Ge), a chemically stable and eco‐friendly element with electronic properties similar to silicon and tin, presents itself as a prospective candidate. This study exhibits the feasibility of CsGeI₃ as a perovskite absorber, tackling significant toxicity and stability issues while achieving competitive efficiency. To realize its full potential, charge transport layers (CTLs) are successively optimized, crucial for reducing recombination losses, enhancing charge extraction, and improving the overall device performance. Utilizing the SCAPS‐1D simulation framework, numerous CTLs (HTLs: CuSCN, CuI, Cu₂O, NiO x , MoO 3 , Spiro‐OMeTAD, P 3 HT) and (ETLs: CeO x , IGZO, ZnSe, TiO₂, WS₂, ZnO, SnO₂) are evaluated to determine the proper CTL pairing. The Au/CuI/CsGeI₃/WS₂/ITO architecture reaches a maximum power conversion efficiency (PCE) of 29.00%. Crucial device properties like absorber thickness (800 nm), defect density (10¹⁴ cm⁻ 3 ), and CTL doping concentrations (HTL: 10¹⁹ cm⁻ 3 , ETL: 10¹⁸ cm⁻ 3 ) are minutely optimized. Because of its suitable band alignment, WS₂ ETL exhibits better electron extraction whilst CuI's elevates hole mobility and reduces interfacial defects. This research achieves strong performance under AM 1.5G illumination, with an open‐circuit voltage = 1.31 V and a fill factor = 84.7%, indicating attenuated non‐radiative losses.