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On efficiency of earth-abundant chalcogenide photovoltaic materials buffered with CdS: The limiting effect of band alignment

Ghorbani, Elaheh (2020):
On efficiency of earth-abundant chalcogenide photovoltaic materials buffered with CdS: The limiting effect of band alignment.
In: Journal of Physics: Energy, IOP Publishing Ltd., pp. 1-7, ISSN 2515-7655,
DOI: 10.1088/2515-7655/ab6942,
[Online-Edition: https://doi.org/10.1088/2515-7655/ab6942],
[Article]

Abstract

Earth-abundant and environmentally-friendly Cu2-II-IV-VI4(II = Sr, Ba; IV = Ge, Sn; VI = S,Se) are considered materials the absorber layers in thin-film solar cells. Attempts to understand and improve optoelectronic properties of these newly emerged absorbers resulted in an efficiency of 5.2% in less than 2 years. However, the energy band alignment at the buffer/absorber interface has not been studied yet; an information which is of crucial importance for designing high performance devices. Therefore, current study focuses on the band offsets between these materials and the CdS buffer. Using core level energies, band discontinuities are calculated at the buffer/absorber interface by first-principles calculations. The results yield a type-II band alignment between all Cu2-II-IV-VI4 absorbers and CdS, hence a negative ΔEc. Adoption of a negative ΔEc (cliff-like conduction band offset) at the buffer/absorber interface, however, gives rise to low open circuit voltage and high interface-related recombinations. Therefore, it is necessary to search for an alternative buffer material that forms a type-I band alignment with these absorbers, where the conduction band minimum and the valence band maximum are both localized on the absorber side.

Item Type: Article
Erschienen: 2020
Creators: Ghorbani, Elaheh
Title: On efficiency of earth-abundant chalcogenide photovoltaic materials buffered with CdS: The limiting effect of band alignment
Language: English
Abstract:

Earth-abundant and environmentally-friendly Cu2-II-IV-VI4(II = Sr, Ba; IV = Ge, Sn; VI = S,Se) are considered materials the absorber layers in thin-film solar cells. Attempts to understand and improve optoelectronic properties of these newly emerged absorbers resulted in an efficiency of 5.2% in less than 2 years. However, the energy band alignment at the buffer/absorber interface has not been studied yet; an information which is of crucial importance for designing high performance devices. Therefore, current study focuses on the band offsets between these materials and the CdS buffer. Using core level energies, band discontinuities are calculated at the buffer/absorber interface by first-principles calculations. The results yield a type-II band alignment between all Cu2-II-IV-VI4 absorbers and CdS, hence a negative ΔEc. Adoption of a negative ΔEc (cliff-like conduction band offset) at the buffer/absorber interface, however, gives rise to low open circuit voltage and high interface-related recombinations. Therefore, it is necessary to search for an alternative buffer material that forms a type-I band alignment with these absorbers, where the conduction band minimum and the valence band maximum are both localized on the absorber side.

Journal or Publication Title: Journal of Physics: Energy
Publisher: IOP Publishing Ltd.
Uncontrolled Keywords: buffer/absorber interface, DFT, earth-abundant chalcogenide, chalcogens
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Materials Modelling
Zentrale Einrichtungen
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ)
Zentrale Einrichtungen > University IT-Service and Computing Centre (HRZ) > Hochleistungsrechner
Date Deposited: 27 Jan 2020 07:06
DOI: 10.1088/2515-7655/ab6942
Official URL: https://doi.org/10.1088/2515-7655/ab6942
Projects: DFG, No. 414750661
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