Beneficial effect of post-deposition treatment in high-efficiency Cu(In,Ga)Se{sub 2} solar cells through reduced potential fluctuations

World-record power conversion efficiencies for Cu(In,Ga)Se{sub 2} (CIGS) solar cells have been achieved via a post-deposition treatment with alkaline metals, which increases the open-circuit voltage and fill factor. We explore the role of the potassium fluoride (KF) post-deposition treatment in CIGS...

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Bibliographic Details
Published inJournal of applied physics Vol. 120; no. 6
Main Authors Jensen, S. A., Glynn, S., Kanevce, A., Dippo, P., Li, J. V., Levi, D. H., Kuciauskas, D.
Format Journal Article
LanguageEnglish
Published United States 14.08.2016
Subjects
CARRIER LIFETIME
CARRIERS
CHARGE CARRIERS
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
COMPUTERIZED SIMULATION
COPPER SELENIDE SOLAR CELLS
DEPOSITION
DIFFUSION
DIFFUSION LENGTH
EFFICIENCY
ELECTRIC POTENTIAL
FILL FACTORS
FLUCTUATIONS
INDIUM SELENIDE SOLAR CELLS
PHOTOLUMINESCENCE
POTASSIUM FLUORIDES
SPECTROSCOPY
THICKNESS
TIME RESOLUTION
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Summary:World-record power conversion efficiencies for Cu(In,Ga)Se{sub 2} (CIGS) solar cells have been achieved via a post-deposition treatment with alkaline metals, which increases the open-circuit voltage and fill factor. We explore the role of the potassium fluoride (KF) post-deposition treatment in CIGS by employing energy- and time-resolved photoluminescence spectroscopy and electrical characterization combined with numerical modeling. The bulk carrier lifetime is found to increase with post-deposition treatment from 255 ns to 388 ns, which is the longest charge carrier lifetime reported for CIGS, and within ∼40% of the radiative limit. We find evidence that the post-deposition treatment causes a decrease in the electronic potential fluctuations. These potential fluctuations have previously been shown to reduce the open-circuit voltage and the device efficiency in CIGS. Additionally, numerical simulations based on the measured carrier lifetimes and mobilities show a diffusion length of ∼10 μm, which is ∼4 times larger than the film thickness. Thus, carrier collection in the bulk is not a limiting factor for device efficiency. By considering differences in doping, bandgap, and potential fluctuations, we present a possible explanation for the voltage difference between KF-treated and untreated samples.
ISSN:0021-8979
1089-7550