Gabriel Graf

Gabriel is a Ph.D. student in the Department of Mechanical Engineering and Materials Science at Duke University in Durham, North Carolina. He is a research associate in the Ab Initio Materials Simulations (AIMS) Group, led by Professor Volker Blum, where he employs first-principles computational methods to investigate the electronic structure and thermodynamic properties of hybrid organic-inorganic perovskites. His research connects the electronic nature of materials with their macroscopic properties, with applications in next-generation solar cells, spintronics, and energy-efficient electronics.

As part of the IRES: Perovskites program, Gabriel is currently hosted at Helmholtz-Zentrum Berlin in the Department of Solution Processing of Hybrid Materials and Devices (SEALM), led by Professor Eva Unger. There, he is investigating the intermediate phases that form during the nucleation and growth of solution-processed hybrid perovskites. A thorough understanding of the associated mechanisms and potential intermediates will enable precise control over nucleation and growth kinetics, thus fulfilling a critical step toward scalable, low cost fabrication of high-quality photovoltaic devices. Gabriel holds a Bachelor of Arts in Chemistry with a minor in Mathematics from Austin College in Sherman, Texas. His background in both synthetic and computational chemistry complements his current work on perovskite nucleation and growth. He is also a fellow in Duke’s AI + Materials National Research Traineeship (aiM-NRT), where he explores the integration of artificial intelligence in materials discovery. In addition to his research, Gabriel has served as a tutor, teaching assistant, and research mentor in chemistry, mathematics, and scientific computing.

Graduate Advisor: Volker Blum (Duke Univeristy)
IRES-Perovskites Host: Eva Unger (Helmholtz Zentrum Berlin)

Computational Investigation of MAPbI₃: Solvent Intermediate Phases

Methylammonium lead iodide (MAPbI₃) is a solution-processable, three-dimensional hybrid organic–inorganic perovskite that has served as a model structure for early research into perovskite-based photovoltaics. The performance of perovskite-based devices depends on film quality, which is governed by the chemical pathway followed during crystallization. Previous literature has revealed the formation of three possible solvent intermediate phases during the crystallization of MAPbI₃ from dimethylformamide solution. The morphological differences between the solvent intermediate phases are maintained in the final perovskite film upon annealing, indicating that some solvent intermediates may be more ideal for forming high-quality perovskite films. While initial work mapping the chemical phase space of this system experimentally is underway, a theoretical treatment of the thermodynamics of this system has not yet been presented. In this report, we discuss the preparation of experimentally refined solvent intermediate crystal structures for chemical phase space mapping using density functional theory. The agreement between experimental and computationally optimized atomic positions and lattice parameters is assessed. Finally, one possible method for the quick identification of solvent intermediate phases in solution without the need for structural refinement is presented.

IRES 2025 Final Report