Crystal Phase and Composition Synergy for Optimized Optoelectronic Performance and Carrier Dynamics in Rb2Au2X6(X=Cl, I) Perovskites

Abstract

All-inorganic gold halide perovskites exhibit excellent stability and tunable bandgaps, positioning them as environmentally sustainable alternatives to organic-inorganic lead halide perovskites in photovoltaics. A mechanistic understanding of how crystal phase and composition engineering regulates multi-level structural and electronic properties—thereby determining charge recombination dynamics and overall performance—requires systematical investigation. In this study, we synthesized Rb2Au2I6 via hydrothermal methods, identifying a previously unreported monoclinic primitive (mP) phase, which is distinct from the known monoclinic C-centered (mC) phase. Additionally, we designed six partially chloride-substituted derivatives of Rb2Au2I6 with distinct space groups to facilitate bandgap tunability and optimize charge carrier dynamics. We employed multiscale simulations, combining first-principles calculations (HSE06 functional with spin-orbit coupling) and device-scale continuum models, to clarify the relationships among different crystal phases, compositional engineering, charge-carrier transport, and device performance. Our analysis identified Rb2Au2Cl4I2 (mC) and Rb2Au2Cl2I4 (mP) as optimal compositions, demonstrating superior thermal stability and optoelectronic properties. Device-scale modeling incorporating cross-scale parameter transfer reveals the kinetic mechanisms linking non-radiative recombination and charge transport imbalance. This approach directly predicts a power conversion efficiency of 20.42% for Rb2Au2Cl4I2 (mC) under operating conditions. This study establishes a comprehensive, mechanism-guided roadmap for the rational design of high-efficiency, stable, all-inorganic gold halide perovskite materials through synergistic crystal phase and composition engineering.