Whittles, TJ;
Veal, TD;
Savory, CN;
Yates, PJ;
Murgatroyd, PAE;
Gibbon, JT;
Birkett, M;
... Dhanak, VR; + view all
(2019)
Band Alignments, Band Gap, Core Levels, and Valence Band States in Cu₃BiS₃ for Photovoltaics.
ACS Applied Materials & Interfaces
, 11
(30)
pp. 27033-27047.
10.1021/acsami.9b04268.
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Text (Article)
Scanlon_Band Alignments, Band Gap, Core Levels, and Valence Band States in Cu₃BiS₃ for Photovoltaics_AAM.pdf - Accepted Version Download (3MB) | Preview |
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Text (Supplementary Material)
Scanlon_Band Alignments, Band Gap, Core Levels, and Valence Band States in Cu₃BiS₃ for Photovoltaics_Supp.pdf - Accepted Version Download (1MB) | Preview |
Abstract
The earth-abundant semiconductor Cu₃BiS₃ (CBS) exhibits promising photovoltaic properties and is often considered analogous to the solar absorbers copper indium gallium diselenide (CIGS) and copper zinc tin sulfide (CZTS) despite few device reports. The extent to which this is justifiable is explored via a thorough X-ray photoemission spectroscopy (XPS) analysis: spanning core levels, ionization potential, work function, surface contamination, cleaning, band alignment, and valence-band density of states. The XPS analysis overcomes and addresses the shortcomings of prior XPS studies of this material. Temperature-dependent absorption spectra determine a 1.2 eV direct band gap at room temperature; the widely reported 1.4–1.5 eV band gap is attributed to weak transitions from the low density of states of the topmost valence band previously being undetected. Density functional theory HSE06 + SOC calculations determine the band structure, optical transitions, and well-fitted absorption and Raman spectra. Valence band XPS spectra and model calculations find the CBS bonding to be superficially similar to CIGS and CZTS, but the Bi^{3+} cations (and formally occupied Bi 6s orbital) have fundamental impacts: giving a low ionization potential (4.98 eV), suggesting that the CdS window layer favored for CIGS and CZTS gives detrimental band alignment and should be rejected in favor of a better aligned material in order for CBS devices to progress.
| Type: | Article |
|---|---|
| Title: | Band Alignments, Band Gap, Core Levels, and Valence Band States in Cu₃BiS₃ for Photovoltaics |
| Location: | United States |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1021/acsami.9b04268 |
| Publisher version: | https://doi.org/10.1021/acsami.9b04268 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | XPS, photoemission, band gap, ionization potential, Cu₃BiS₃, density functional theory |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10079314 |
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