Invited Seminar (Group Prof. Núria López) – Dr. Franziska S. Hegner

📍 ICIQ Library

⏰  13:00 h

The Impact of Structural Dynamics in Photoactive Materials

Franziska Simone Hegner

Technical University of Munich, School of Natural Sciences and Walter Schottky Institute

Amid the growing urgency for sustainable energy solutions, the quest for advanced solar harvesting materials has become more pressing than ever. The behaviour of materials under device-relevant operational conditions is largely affected by finite-temperature atomic motions. These dynamic motions influence electronic structures, phase stabilities, and transport characteristics, ultimately determining the industrial relevance of the material.

In this talk, we will focus on the structural dynamics of the novel nitride semiconductor CuTaN2, which is particularly promising for solar energy conversion and representative for the wider class of light absorbing ternary nitrides. We employ first-principles molecular dynamics, Raman spectroscopy, and temperature-dependent X-ray diffraction to investigate the nature of the atomic vibrations and their consequences for the macroscopic physical properties. The results reveal that the dynamics are strongly anharmonic, indicating deviations from the conventional description of normal modes or phonons in this material. At the macroscale, these anharmonic induce compression upon heating and, significantly for solar energy harvesting, they contribute to a substantial bandgap opening by altering orbital overlaps close to the Fermi level.

This study highlights the potential of CuTaN₂, and potentially other related nitrides, as optimal materials for photovoltaic and photoelectrochemical energy conversion, and emphasizes the pivotal role of structural dynamics in defining key properties of emerging photoactive materials.