Digital workflow optimization of van der Waals methods for improved halide perovskite solar materials

Abstract

Hybrid organic–inorganic metal halide perovskites are low-cost and highly efficient materials used in solar cell devices. However, the intricacies of perovskites that merge organic cations with inorganic frameworks necessitate further elucidation, particularly from the long-range van der Waals perspective. Here, we scrutinize the van der Waals (vdW) methods by conceptualizing organic cations for XH₄PbI₃ and CH₃XH₃PbI₃ prototype perovskites (X = N, P, As, and Sb), to investigate the thermodynamic stability. To handle the enormous amount of raw data generated from DFT + vdW + SOC with DFT-1/2 (quasi-particle correction method), we have used the SimStack workflow framework, which enhanced the efficiency, reproducibility, and data transferability. The results reveal the critical role of the organic cations, inferred from ionic radius estimates and documented electronegativity, in elucidating the accommodation of symmetric XH₄⁺ or asymmetric CH₃XH₃⁺ cations within the limited volumes of cuboctahedral cavities. The discrepancy in the ionic size within the XH₄PbI₃ (CH₃XH₃PbI₃) group positions NH₄PbI₃ (CH₃NH₃PbI₃) outside (within) the stable perovskite region suggests the theoretical viability of perovskites containing phosphonium, arsonium, and stibonium beyond CH₃NH₃PbI₃. As we move from N to Sb, the organic cation's properties, such as ionic radius and electronegativity, affect the thermodynamic stability and local geometry of octahedra, directly influencing the band gaps.