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在材料科学蓬勃发展的进程中，清洁能源需求的激增使金属卤化物钙钛矿（MHPs）材料在光伏领域备受瞩目，其功率转换效率超 26%。然而，MHPs的内在化学不稳定性是实现持久器件的一个挑战，制约了耐用光伏设备的发展。这也促使合金化策略出现，如将Cs阳离子与有机候选物混合形成A1−xCsxPbI3（A = MA，FA）。MHPs 具有复杂多晶型特性，其局部结构与全局Pm3m空间群不同，存在多种低对称结构基序，难以通过 XRD 区分，且它们对合金热力学稳定性和电子性质影响的匮乏研究。分析MHPs合金阳离子混合影响时，虽有理论方法，但保持从头算准确性面临挑战，因其涉及相对论校正。因此，开发一套自动化流程框架，对捕获这种多晶型特性并研相关电子结构性质极为迫切。
Fig. 1 | SimStack workflow.
来自巴西巴拉那联邦大学化学系的LuisOctavio de Araujo等，提出了一种基于 SimStack 框架的自动化工作流程，运用广义准化学近似（GQCA）等方法，实现了对A1-xCsxPbI3（A=MA，FA）伪立方合金全面深入的研究。该流程可精确计算合金热力学性质、相图、光电特性及功率转换效率，并纳入关键相对论效应。作者系统分析了有机和无机阳离子混合对合金结构与电子特性的影响，揭示了阳离子特性对格拉泽旋转及合金稳定性的作用机制，得到不同成分合金的稳定条件及相关热力学数据，并计算出了不同合金在特定成分下的功率转换效率，如MA1-xCsxPbI3（0.50<x<1.00）和A1-xCsxPbI3（0.0<x<0.20）在室温下的高效率表现。
Fig. 12 | Structures. a Pictorialrepresentation of the APbI3 (CsPbI3) 2 × 2 × 2 supercell expansion.
Automated workflow for analyzing thermodynamic stability in polymorphic perovskite alloys
Luis Octavio de Araujo, Celso R. C. Rêgo, Wolfgang Wenzel, Maurício Jeomar Piotrowski, Alexandre Cavalheiro Dias & Diego Guedes-Sobrinho
In 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.