Thin film chalcogenide absorbing Materials for solar energy conversion

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Professor Ahmed Ennaoui
Chairman of the scientific council
Institute for Research in Solar Energy and New Energies (IRESEN)

IEEE member

ISES member

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ABSTRACT:

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Binary, ternary and quaternary thin film chalcogenide materials with their direct gap and high absorption coefficients are used as photoactive materials for solar energy conversion e.g. photovoltaic solar cells for the production of electricity from the sun with short energy payback time and minimum use of high purity materials or electrode for (photo)electro-catalysis, such as water splitting. This can be achieved with minimized material use and the possibility for using low cost non-vacuum techniques. Chalcopyrite Cu(In,Ga)(S,Se)2 (CIGSS) with record efficiencies for small cells of 22.3 % and for production size modules of 16.5 % are already demonstrated. The production cost is already comparable to crystalline Si and approx. 3 GWp CIGSS modules were shipped worldwide [1]. Kesterite Cu2ZnSn(S,Se)4 (CZTSS) is another emerging material, basically, derived from CuInS2 (CIS) by replacing In(III) with two abundant and non-toxic elements Zn(II) and Sn(IV). The maximum efficiency achieved so far with CZTS thin film solar cell is closed to 13% using a combination of wet chemical processing and annealing [2]. Non-vacuum processes can in many cases match the coating quality of vacuum-based processes, while providing significant advantages in capital costs, operating costs, functional complexity, and competitive scale. A particularly attractive non-vacuum film deposition processes is based on Drop on Demand (D-O-D) inkjet printing technology with reduced raw material waste by mostly 90 percent compared to the vacuum process. However, the challenging issue for inkjet printing is a large scale production of technically printable ink that can be scalable. As matter of fact, in same step of solar cell processing the vacuum process step still a must to produce high quality absorbers. Inkjet printing is also used for processing perovskite and Cu(In,Ga)(S,Se)2 (CIGS) as top and bottom cells, respectively. Perovskite/CIGS tandem thin-film solar is a new generation of solar cell converting all sunlight spectrum into electricity. In this keynote we will highlights the potential of thin film chalcogenide for solar energy conversion with particular interest to photovoltaics and water splitting. We will present our proof of concept, for the fabrication of CIGS and CZTS-based thin film solar cells which consists of (1) formulation of suitable inorganic ink that can be easily scalable, (2) deposition of precursor films and (3) annealing step for the fabrication of high quality absorbers [3,4]. We will also discuss the material aspect of water splitting, the kinetic and thermodynamic barriers associated with the water redox reactions and the additional criteria that need to be considered for a successful solar water-splitting system.

 

[1] http://cigs-pv.net/wortpresse/ wp-content/uploads/2015/12/ CIGS-WhitePaper.pdf

[2] http://www.solar-frontier.com/ eng/news/2013/C026764.html

[3] X. Lin , J. Kavalakkatt, M. Lux-Steiner, and A. Ennaoui.

Inkjet-Printed Cu2ZnSn(S,Se)4 Solar Cells, Advanced Sciences (2015), Vol. 2, Issue 6

[4] X. Lin, A. Ennaoui, R. Klenk, S. Fiechter, A. Ennaoui, M. Lux-Steiner.

11.3% efficiency Cu (In, Ga)(S,Se)2 thin film solar cells via drop-on-demand inkjet printing, Energy & Environmental Science (2016) 9 (6), 2037-2043.