Automated workflow for analyzing thermodynamic stability in polymorphic perovskite alloys

Abstract

AbstractIn this first-principles investigation, we explore the polymorphic features of pseudo-cubic alloys, focusing on the impact of mixing organic and inorganic cations on their structural and electronic properties, configurational disorder, and thermodynamic stability. Employing an automated cluster expansion within the generalized quasichemical approximation (GQCA), our results reveal how the effective radius of the organic cation (rMA = 2.15 Å, rFA = 2.53 Å) and its dipole moment (μMA = 2.15 D, μFA = 0.25 D), influences Glazer’s rotations in the A1−xCsxPbI3 (A = MA, FA) sublattice, with MA-based alloy presenting a higher critical temperature (527 K) and being stable for x > 0.60 above 200 K, while its FA analog has a lower critical temperature (427.7 K) and is stable for x < 0.15 above 100 K. Additionally, polymorphic motifs magnify relativistic effects, impacting the thermodynamic behavior of the systems. Our methodology leverages the SimStack framework, an automated scientific workflow that enables the nuanced modeling of polymorphic alloys. This structured approach allows for comprehensive calculations of thermodynamic properties, phase diagrams, optoelectronic insights, and power conversion efficiencies while meticulously incorporating crucial relativistic effects like spin-orbit coupling (SOC) and quasi-particle corrections. Our findings advocate for the rational design of thermodynamically stable compositions in solar cell applications by calculating power conversion efficiencies using a spectroscopic limited maximum efficiency model, from which we obtained high efficiencies of about 28% (31–32%) for MA1−xCsxPbI3 with 0.50 < x < 1.00 (FA1−xCsxPbI3 with 0.0 < x < 0.20) as thermodynamically stable compositions at room temperature. The workflow’s significance is highlighted by a Colab-based notebook, which facilitates the analysis of raw data output, allowing users to delve into the physics of these complex systems. Our work underscores the pivotal role of composition and polymorphic degrees in determining the stability and optoelectronic properties of MHP alloys. It demonstrates the effectiveness of the SimStack workflow in advancing our understanding of these materials.