Journal article
Experimental and First-Principles Spectroscopy of Cu2SrSnS4 and Cu2BaSnS4 Photoabsorbers
Surface Physics and Catalysis, Department of Physics, Technical University of Denmark1
VISION – Center for Visualizing Catalytic Processes, Centers, Technical University of Denmark2
University College London3
Department of Photonics Engineering, Technical University of Denmark4
Structured Electromagnetic Materials, Department of Photonics Engineering, Technical University of Denmark5
Department of Physics, Technical University of Denmark6
Department of Health Technology, Technical University of Denmark7
Drug Delivery and Sensing, Department of Health Technology, Technical University of Denmark8
Nanoprobes, Drug Delivery and Sensing, Department of Health Technology, Technical University of Denmark9
Center for Nanostructured Graphene, Centers, Technical University of Denmark10
...and 0 moreCu2BaSnS4 (CBTS) and Cu2SrSnS4 (CSTS) semiconductors have been recently proposed as potential wide band gap photovoltaic absorbers. Although several measurements indicate that they are less affected by band tailing than their parent compound Cu2ZnSnS4, their photovoltaic efficiencies are still low. To identify possible issues, we characterize CBTS and CSTS in parallel by a variety of spectroscopic methods complemented by first-principles calculations.
Two main problems are identified in both materials. The first is the existence of deep defect transitions in low-temperature photoluminescence, pointing to a high density of bulk recombination centers. The second is their low electron affinity, which emphasizes the need for an alternative heterojunction partner and electron contact.
We also find a tendency for downward band bending at the surface of both materials. In CBTS, this effect is sufficiently large to cause carrier-type inversion, which may enhance carrier separation and mitigate interface recombination. Optical absorption at room temperature is exciton-enhanced in both CBTS and CSTS.
Deconvolution of excitonic effects yields band gaps that are about 100 meV higher than previous estimates based on Tauc plots. Although the two investigated materials are remarkably similar in an idealized, defect-free picture, the present work points to CBTS as a more promising absorber than CSTS for tandem photovoltaics.
Language: | English |
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Publisher: | American Chemical Society |
Year: | 2020 |
Pages: | 50446-50454 |
ISSN: | 19448252 and 19448244 |
Types: | Journal article |
DOI: | 10.1021/acsami.0c14578 |
ORCIDs: | Crovetto, Andrea , Fischer, Moritz , Nielsen, Rasmus , Rindzevicius, Tomas , Stenger, Nicolas , Chorkendorff, Ib , Vesborg, Peter Christian Kjærgaard , 0000-0002-9052-7484 and 0000-0001-9174-8601 |