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 P1̅(P1̅ – II; P1̅ – 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.