Deposition of Pb‐Free CsGeI _{3− <i>x</i>} Cl _<i>x</i> in Atmospheric Conditions, and Exploring Suitable Carrier Transport Materials for Improving its Power Conversion Efficiency: A Numerical Simulation Approach

Pb‐free mixed‐halide perovskites emerge as alternative to Pb‐based perovskites due to their environmentally friendly and intriguing optoelectronic properties. Pb‐free thin film of CsGeI 3 – x Cl x is deposited in atmospheric conditions, and it is comprehensively characterized. Scanning electron microscopy and X‐ray diffraction results confirm trigonal structure. Energy‐dispersive X‐ray and Fourier transform infrared inspections confirm film compositions: Cs, Ge, I, and Cl. Value of E g and α is to be1.66 eV and &gt;10 5 cm −1 . Theoretically, solar cell performance is calculated by Solar Cell Capacitance Simulator‐1D software. Absorber thickness greatly impacts photovoltaic parameters rather than combinations of various electron‐ and hole‐transport layers (ETLs, HTLs). IGZO and CBTS can be suitable as ETL, HTL for CsGeI 3 – x Cl x . Optimized thickness of CsGeI 3 – x Cl x , ETL (IGZO), and HTL (CBTS) layers is to be 1.0, 0.05, and 0.10 μm. An efficiency ≈12.35% is exhibited by the proposed Se/CBTS/CsGeI 3 – x Cl x /CdS/IGZO/ETL/FTO/Ag device for as‐deposited film, which reaches 14.78% for optimum configuration. This study ensures that the performance actively depends on absorber, electron affinity, bandgap, HTL, ETL, parasitic resistances, defects/carriers density, temperature, and so on. Theoretically, CsGeI 3 – x Cl x is an excellent photocatalyst for H 2 and O 2 production. Therefore, these favorable characteristics make it a potential alternative to Pb‐halide perovskites for photovoltaic and optoelectronic applications.