First-principles design and photovoltaic evaluation of alkali-based M3ClO anti-perovskites for high-efficiency lead-free solar cells

The global demand for efficient and non-toxic alternatives to lead-based perovskites has spurred interest in novel materials for photovoltaic applications. This work presents a detailed first-principles investigation of the structural, electronic, mechanical, optical, photonic, and thermodynamic properties of alkali-based anti-perovskites M₃ClO (M = K, Rb, Cs, Fr), complemented by SCAPS-1D device simulations. Structural optimization confirms the thermodynamic and mechanical stability of K₃ClO, Rb₃ClO, and Cs₃ClO, while phonon dispersion indicates dynamical robustness in all but Fr₃ClO. The electronic band structures reveal tunable band gaps, with K₃ClO (1.97 eV) and Rb₃ClO (1.566 eV) displaying optimal values for visible light absorption. Optical analyses demonstrate strong UV-visible absorption, low reflectivity, and high dielectric response, particularly in K₃ClO, which enhances its suitability as a solar absorber. Mechanical assessments show that Cs₃ClO and Fr₃ClO possess superior ductility and flexibility, which is favorable for wearable photovoltaic devices. Thermodynamic analyses affirm the compounds’ stability under high temperatures, supporting their potential in durable solar technologies. The optimized device parameters, including absorber thickness, shallow acceptor density, total defect density, and total interface defect density, were employed to perform QE and J–V simulations using SCAPS-1D. Device-level simulations predict power conversion efficiencies of 25.39% for K₃ClO, 23.31% for Rb₃ClO, and 19.72% for Cs₃ClO. These results highlight K₃ClO, Rb₃ClO and Cs₃ClO as promising absorber materials for next-generation, environmentally friendly solar cells. Overall, the study emphasizes the critical connection between intrinsic material properties and practical photovoltaic performance.