All-Inorganic CsPbI_xBr_3−x Perovskite Solar Cells: Crystal Anisotropy Effect

Understanding the crystal anisotropy effect of materials on optical and electrical properties is crucial for further comprehension of the device operating mechanism and device performance improvement. In this study, a detailed theoretical analysis is performed to explore the crystal anisotropy effect on the performance of perovskite solar cells by employing state-of-the-art multiscale simulations connecting from the material (first-principle theory) to the device (drift-diffusion model). According to the results obtained from first-principle calculation, the mobility and absorption coefficient of CsPbIBr₂ and CsPbI₂Br along the [001] orientation are larger than those along the [100] orientation, suggesting that the transport properties and optical properties along the [001] orientation are superior to those along the [100] orientation. According to the results obtained from the drift-diffusion model, owing to the superior optical and transport characters along the [001] direction, the optimal power conversion efficiencies (PCEs) of CsPbI₂Br (18.88%) and CsPbIBr₂ (16.42%) solar cells can be obtained. In addition, the two-terminal CsPbI_xBr_3-x/silicon tandem solar cell is also investigated. By utilizing CsPbIBr₂/silicon and CsPbI₂Br/silicon tandem structures along the [001] orientation, ultrahigh efficiencies are achieved up to 26.32% and 31.39%, respectively. Therefore, the [001] crystal orientation of CsPbIBr₂ and CsPbI₂Br is more suitable for further applications of optoelectronic devices.