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ACS Appl Mater Interfaces. 2016 Mar 2;8(8):5261-72. doi: 10.1021/acsami.5b10789. Epub 2016 Feb 16.

Carbon-Impurity Affected Depth Elemental Distribution in Solution-Processed Inorganic Thin Films for Solar Cell Application.

Rehan S1,2, Kim KY1, Han J1,2, Eo YJ1, Gwak J1, Ahn SK1, Yun JH1,2, Yoon K1, Cho A1,2, Ahn S1,2.

Author information

1
Photovoltaic Laboratory, Korea Institute of Energy Research , Daejeon 305-343, Korea.
2
Department of Renewable Energy Engineering, Korea University of Science and Technology (UST) , Daejeon 305-350, Korea.

Abstract

A common feature of the inorganic thin films including Cu(In,Ga)(S,Se)2 fabricated by nonvacuum solution-based approaches is the doubled-layered structure, with a top dense inorganic film and a bottom carbon-containing residual layer. Although the latter has been considered to be the main efficiency limiting factor, (as a source of high series resistance), the exact influence of this layer is still not clear, and contradictory views are present. In this study, using a CISe as a model system, we report experimental evidence indicating that the carbon residual layer itself is electrically benign to the device performance. Conversely, carbon was found to play a significant role in determining the depth elemental distribution of final film, in which carbon selectively hinders the diffusion of Cu during selenization, resulting in significantly Cu-deficient top CISe layer while improving the film morphology. This carbon-affected compositional and morphological impact on the top CISe films is a determining factor for the device efficiency, which was supported by the finding that CISe solar cells processed from the precursor film containing intermediate amount of carbon demonstrated high efficiencies of up to 9.15% whereas the performances of the devices prepared from the precursor films with very high and very low carbon were notably poor.

KEYWORDS:

carbon-residue layer; chalcopyrite; diffusion; nonvacuum; ohmic; photovoltaics; resistance; solution deposition

PMID:
26817680
DOI:
10.1021/acsami.5b10789

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