Beginner’s Guide to Interpreting Defect and Defect Level Diagrams

Point defects are ubiquitous in materials and play a critical role in determining their electrical, optical, ion-transport, and other properties, making them key to the performance of materials in energy applications. First-principles defect calculations, particularly those based on density functional theory, are powerful tools for predicting defect energetics and associated electronic properties. However, the results are often communicated through defect formation energy diagrams and defect level diagrams, which can be challenging to interpret for researchers who do not specialize in defect physics. This Tutorial provides a practical accessible guide for understanding and interpreting these diagrams, with a focus on materials with a band gap—semiconductors and insulators. Aimed at experimentalists and computationalists new to defect analysis, the Tutorial explains how to extract key physical insights from defect diagrams, such as defect and carrier concentrations, dopability, midgap states, and charge localization. By demystifying the language and visuals of defect calculations, this guide seeks to bridge the gap between theory and experiments, enabling broader use of defect data in the rational design of functional materials for energy applications and beyond.