In-line deposited Cu(In,Ga)Se2 solar cells: influence of deposition temperature and Na co-evaporation on carrier collection

We investigated the influence of deposition temperature and sodium co-evaporation on the carrier collection properties of Cu(In,Ga)Se2 solar cells. I-V and bias-dependent quantum efficiency measurements were performed on cells deposited at 550 and 420 DGC with and without sodium co-evaporation. A re...

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Bibliographic Details
Published in:Thin solid films 2004-03, Vol.451-452 (Complete), p.175-178
Main Authors: Lammer, M., Kniese, R., Powalla, M.
Format: Article
Language:English
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Summary:We investigated the influence of deposition temperature and sodium co-evaporation on the carrier collection properties of Cu(In,Ga)Se2 solar cells. I-V and bias-dependent quantum efficiency measurements were performed on cells deposited at 550 and 420 DGC with and without sodium co-evaporation. A reduction of deposition temperature leads to a deterioration of solar cell output parameters due to reduced sodium diffusion from the substrate as well as an increased grain boundary density. Bias-dependent quantum efficiency measurements reveal that these effects lead to a decrease of minority carrier diffusion length. When sodium is co-evaporated during absorber growth at low Tdep, solar cells with VOC and FF values in the range of high-temperature-deposited devices are realised. However, jsc is not enhanced. Bias-dependent quantum efficiency measurements show that an applied bias voltage does not influence the quantum efficiency curve when sodium is co-evaporated during CIGS growth. The origin of this behaviour is not completely understood.
ISSN:0040-6090
DOI:10.1016/j.tsf.2003.10.107