On the origin of band-tails in kesterite

Kesterite Cu2ZnSn(SxSe1−x)4 is an attractive earth-abundant material for low-cost thin film photovoltaics with the capability to achieve power production in the terawatt range and therefore to supply a significant part of the global electricity needs. Despite its advantageous optical and electrical...

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Bibliographic Details
Published in:Solar energy materials and solar cells 2018-06, Vol.179, p.142-151
Main Authors: Rey, G., Larramona, G., Bourdais, S., Choné, C., Delatouche, B., Jacob, A., Dennler, G., Siebentritt, S.
Format: Article
Language:English
Subjects:
Band-tail
Chemical composition
Composition
CZTSe
CZTSSe
Electric power generation
Electrical properties
Electricity
Fluctuations
Kesterite
Optical properties
Organic chemistry
Photoluminescence
Photovoltaic cells
Photovoltaics
Power supply
Solar cells
Studies
Trace elements
Zinc
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Summary:Kesterite Cu2ZnSn(SxSe1−x)4 is an attractive earth-abundant material for low-cost thin film photovoltaics with the capability to achieve power production in the terawatt range and therefore to supply a significant part of the global electricity needs. Despite its advantageous optical and electrical properties for photovoltaic applications, the large band tailing causes voltage losses that limit the efficiency of kesterite-based devices. Here we show that the band-tailing originates mainly from band-gap fluctuations attributable to chemical composition variations at nanoscale; while electrostatic fluctuations play a lesser role. Absorption measurement reveal that the Cu-Zn disorder, always present in kesterite Cu2ZnSn(SxSe1−x)4, is not the main source of the large band tailing. Instead defect clusters having a significant impact on the band-edge energies, e.g. [2CuZn−+SnZn2+], are proposed as the main origin for the kesterite band tail. •The band-tailing in kesterite originates mainly from band-gap fluctuation.•Electrostatic fluctuations play a lesser role.•Absorption data reveal that the Cu-Zn disorder is not the main source of band tail.•Defects with significant impact on the band-edges are proposed as the main source.
ISSN:0927-0248
1879-3398
DOI:10.1016/j.solmat.2017.11.005