SKM 2023 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: 2D Materials I: Electronic Structure

O 30.11: Vortrag

Dienstag, 28. März 2023, 13:00–13:15, GER 37

Structure and electronic-optical properties of polymeric carbon nitride — •Changbin Im, Björn Kirchhoff, and Timo Jacob — Ulm University, Institute of Electrochemistry, Ulm, Germany

Understanding of the electronic structure and optical properties of polymeric carbon nitrides (PCNs) is of key interest in order to exploit their photo-physical and photo-electrocatalytic capabilities. The numerous defects of typical PCNs, however, present a limitation to computational studies that aim to improve our fundamental understanding of this material class. Here, we demonstrate a systematic thermodynamic study and structural characterization of various heptazine based-PCN models from the viewpoint of electronic and optical properties obtained with hybrid density functional theory (DFT). Our calculations reveal the key structural factors (degree of condensation, interlayer distance, corrugation) that govern the formation of various PCN motifs and their optical properties.[1] We discuss how each of the key factors influences the electronic structure of PCNs. We also suggest the concept of exciton binding energy in PCNs and discuss the polaronic interactions between heptazine units due to the localized exciton nature. Furthermore, we disclose a failure of GGA in the description of correlated electrons that underestimates the energy of the conjugated electrons comparing hybrid DFT. From the results, we could not only deduce a more complete model for the diverse PCN motifs but could additionally derive fundamental trends for future material optimization.

[1] Im, C. et al. (2022). http://arxiv.org/abs/2208.02582 submitted.