Revealing the Potential Crystal Structures of Earth-Abundant Nontoxic Photovoltaic CuBiI₄

Ternary metal halides are important photoelectric materials with proven high performance as absorber layers in solar cells. In this paper, we explore the crystal structures of the low-cost, nontoxic, earth-abundant absorber CuBiI4 belonging to Bi-based copper halide (CuBiI). By performing a global search for minimum energy structures based on the evolutional genetic algorithm, fifteen crystal structures of CuBiI4 with low energy are predicted. The energetics and mechanical and dynamical stability of these structures are comprehensively investigated. The calculation results show that two P1¯ (P1¯ - II; P1¯ - III) structures and one P21/m structure are energetically favorable and have good dynamical and mechanical stability. The simulated X-ray diffraction curves of the P21/m structure are highly consistent with the experimental data. Meanwhile, the three CuBiI4 structures all have high photoelectric conversion efficiency (greater than 17%), indicating their potential as absorption layer materials for high-performance solar cells.