Abstract: All-inorganic germanium (Ge)-based perovskite solar cells (PSCs) have attracted significant attention due to their environmental friendliness and excellent optoelectronic properties. However, limited by high internal defect densities and short carrier diffusion lengths, traditional single-junction devices suffer from severe bulk recombination losses, resulting in power conversion efficiencies (PCE) far below the theoretical limit. In this study, a method of constructing an n-p homojunction within the CsGeI₃ absorption layer is proposed to enhance the built-in electric field and improve carrier transport efficiency. Utilizing SCAPS-1D software, key parameters such as absorption layer thickness and doping concentrations were systematically optimized. By comparing the energy band evolution, built-in electric field distribution, and carrier recombination kinetics of single-junction and homojunction structures, the fundamental advantages of the homojunction design in suppressing Shockley-Read-Hall recombination and enhancing charge collection efficiency are revealed. The results demonstrate that when the n-type layer thickness is 100 nm with a doping concentration of 1.0×10¹⁸ cm⁻³, and the p-type layer thickness is 650 nm with a doping concentration of 1.0×10¹⁸ cm⁻³, the device achieves a peak PCE of 27.68%, significantly outperforming traditional single-junction devices. This work not only provides a new physical pathway to overcome the carrier transport bottleneck in lead-free perovskites but also offers crucial theoretical support and design strategies for fabricating high-efficiency, eco-friendly all-inorganic PSCs.