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Design of optimal buffer layers for CuInGaSe2 thin-film solar cells (Conference Presentation)
Author(s): Vincenzo Lordi; Joel B. Varley; Xiaoqing He; Angus A. Rockett; Jeff Bailey; Geordie H. Zapalac; Neil Mackie; Dmitry Poplavskyy; Atiye Bayman
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Paper Abstract

Optimizing the buffer layer in manufactured thin-film PV is essential to maximize device efficiency. Here, we describe a combined synthesis, characterization, and theory effort to design optimal buffers based on the (Cd,Zn)(O,S) alloy system for CIGS devices. Optimization of buffer composition and absorber/buffer interface properties in light of several competing requirements for maximum device efficiency were performed, along with process variations to control the film and interface quality. The most relevant buffer properties controlling performance include band gap, conduction band offset with absorber, dopability, interface quality, and film crystallinity. Control of an all-PVD deposition process enabled variation of buffer composition, crystallinity, doping, and quality of the absorber/buffer interface. Analytical electron microscopy was used to characterize the film composition and morphology, while hybrid density functional theory was used to predict optimal compositions and growth parameters based on computed material properties. Process variations were developed to produce layers with controlled crystallinity, varying from amorphous to fully epitaxial, depending primarily on oxygen content. Elemental intermixing between buffer and absorber, particularly involving Cd and Cu, also is controlled and significantly affects device performance. Secondary phase formation at the interface is observed for some conditions and may be detrimental depending on the morphology. Theoretical calculations suggest optimal composition ranges for the buffer based on a suite of computed properties and drive process optimizations connected with observed film properties. Prepared by LLNL under Contract DE-AC52-07NA27344.

Paper Details

Date Published: 2 November 2016
PDF: 1 pages
Proc. SPIE 9936, Thin Films for Solar and Energy Technology VIII, 993609 (2 November 2016); doi: 10.1117/12.2237243
Show Author Affiliations
Vincenzo Lordi, Lawrence Livermore National Lab. (United States)
Joel B. Varley, Lawrence Livermore National Lab. (United States)
Xiaoqing He, Univ. of Illinois at Urbana-Champaign (United States)
Angus A. Rockett, Univ. of Illinois at Urbana-Champaign (United States)
Jeff Bailey, MiaSolé Hi-Tech Corp. (United States)
Geordie H. Zapalac, MiaSolé Hi-Tech Corp. (United States)
Neil Mackie, MiaSolé Hi-Tech Corp. (United States)
Dmitry Poplavskyy, MiaSolé Hi-Tech Corp. (United States)
Atiye Bayman, MiaSolé Hi-Tech Corp. (United States)


Published in SPIE Proceedings Vol. 9936:
Thin Films for Solar and Energy Technology VIII
Michael J. Heben; Mowafak M. Al-Jassim, Editor(s)

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Design of optimal buffer layers for CuInGaSe2 thin-film solar cells (Conference Presentation)



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