Theoretical Advances and Future Perspectives of All-Inorganic Germanium-Based Perovskites

Against the backdrop of intensifying global energy challenges, perovskite materials with remarkable photovoltaic potential in solar cell development continue to face dual constraints: lead toxicity and poor stability in organic-inorganic hybrid structures. As a promising alternative, all-inorganic germanium-based perovskites have garnered significant attention in recent years. Given the absence of systematic theoretical investigations on germanium-based systems, this review comprehensively examines recent theoretical advances in this emerging field. The discussion encompasses three key aspects: (i) structural characteristics, including Ge-induced lattice configurations, tolerance factors, and phase stability; (ii) optoelectronic properties, particularly Shockley-Queisser limit evaluations, theoretical bandgap predictions, germanium-induced optoelectronic modulation, and related exploratory investigations; (iii) supplementary properties such as mechanical response, pyroelectric behavior, and ferroelectric functionality. Theoretical investigations reveal distinctive advantages, notably enhanced structural stability through non-centrosymmetric distortions and defect-dependent conductivity under various configurations. However, challenges persist in fabrication techniques and power conversion efficiency optimization. The review concludes by proposing four strategic research directions: discovery of novel perovskite derivatives, optimization of compositional engineering, atomistic-level defect analysis, and exploration of multifunctional applications, providing a roadmap for future investigations in this burgeoning field.