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GeSe: optical spectroscopy and theoretical study of a van der Waals solar absorber

DOI: 10.1021/acs.chemmater.0c00453 DOI Help

Authors: Philip A. E. Murgatroyd (University of Liverpool) , Matthew J. Smiles (University of Liverpool) , Christopher N. Savory (University College London) , Thomas P. Shalvey (University of Liverpool) , Jack E. N. Swallow (University of Liverpool) , Nicole Fleck (University of Liverpool) , Craig M. Robertson (University of Liverpool) , Frank Jaeckel (University of Liverpool) , Jonathan Alaria (University of Liverpool) , Jonathan D. Major (University of Liverpool) , David O. Scanlon (University College London; Diamond Light Source) , Tim D. Veal (University of Liverpool)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials

State: Published (Approved)
Published: March 2020

Abstract: The van der Waals material GeSe is a potential solar absorber, but its optoelectronic properties are not yet fully understood. Here, through a combined theoretical and experimental approach, the optoelectronic and structural properties of GeSe are determined. A fundamental absorption onset of 1.30 eV is found at room temperature, close to the optimum value according to the Shockley-Queisser detailed balance limit, in contrast to previous reports of an indirect fundamental transition of 1.10 eV. The measured absorption spectra and first-principles joint density of states are mutually consistent, both exhibiting an additional distinct onset $\sim$0.3~eV above the fundamental absorption edge. The band gap values obtained from first-principles calculations converge, as the level of theory and corresponding computational cost increases, to 1.33 eV from the quasiparticle self-consistent GW method, including the solution to the Bethe-Salpeter equation. This agrees with the 0~K value determined from temperature-dependent optical absorption measurements. Relaxed structures based on hybrid functionals reveal a direct fundamental transition in contrast to previous reports. The optoelectronic properties of GeSe are resolved with the system described as a direct semiconductor with a 1.30 eV room temperature band gap. The high level of agreement between experiment and theory encourages the application of this computational methodology to other van der Waals materials.

Subject Areas: Chemistry, Materials


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