DocumentCode
739918
Title
Improved Photocurrent in Cu(In,Ga)Se2 Solar Cells: From 20.8% to 21.7% Efficiency with CdS Buffer and 21.0% Cd-Free
Author
Friedlmeier, Theresa Magorian ; Jackson, Philip ; Bauer, Andreas ; Hariskos, Dimitrios ; Kiowski, Oliver ; Wuerz, Roland ; Powalla, Michael
Author_Institution
Zentrum fur Sonnenenergie-und Wasserstoff-Forschung Baden-Wurttemberg (ZSW), Stuttgart, Germany
Volume
5
Issue
5
fYear
2015
Firstpage
1487
Lastpage
1491
Abstract
New processing developments in the Cu(In,Ga)Se2 (CIGS)-based solar cell technology have enabled best cell efficiencies to exceed 21%. The key innovation involves the alkali post-deposition treatment (PDT) of the CIGS film. Furthermore, the range of optimal CIGS growth parameters and the minimal thickness of the CdS buffer layer is affected by the process modifications. In 2013, we reported a 20.8% record device with PDT. Later optimizations, e.g., in the composition profile and CdS buffer layer thickness as discussed in this study, enabled us to increase the photocurrent density with only a slight loss in open-circuit voltage and unchanged fill factor, resulting in the current world record of 21.7% efficiency. Furthermore, a record efficiency of 21.0% could be achieved with a Cd-free Zn(O,S) buffer layer. This contribution presents measurements, simulations, and a discussion of the photocurrent increase.
Keywords
II-VI semiconductors; buffer layers; cadmium compounds; copper compounds; current density; gallium compounds; indium compounds; photoconductivity; semiconductor device models; semiconductor thin films; solar cells; ternary semiconductors; wide band gap semiconductors; zinc compounds; Cd-free Zn(O,S) buffer layer; CdS; Cu(InGa)Se2; Zn(OS); alkali post-deposition treatment; cell efficiencies; composition profile; fill factor; minimal CdS buffer layer thickness; open-circuit voltage; optimal growth parameters; photocurrent density; processing developments; solar cell technology; Buffer layers; Photoconductivity; Photonic band gap; Photovoltaic cells; Photovoltaic systems; Surface treatment; Buffer layers; Cu(In; Ga)Se2 (CIGS); coevaporation; heterojunctions; photovoltaic cells; scanning electron microscopy; short-circuit currents; thin-film devices;
fLanguage
English
Journal_Title
Photovoltaics, IEEE Journal of
Publisher
ieee
ISSN
2156-3381
Type
jour
DOI
10.1109/JPHOTOV.2015.2458039
Filename
7182738
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