Challenges in the deposition of (Ag, Cu)(In, Ga)Se2 absorber layers for thin-film solar cells. (14th January 2021)

• Record Type: Journal Article
• Authors: Essig, Stephanie; Paetel, Stefan; Friedlmeier, Theresa Magorian; Powalla, Michael
• Is Part Of: JPhys materials. Volume 4:Number 2(2021)
• Publication Date: 2021-01-14
• Subjects: three-stage co-evaporation -- (Ag, Cu)(In, Ga)Se2 -- solar cells -- chalcopyrite; Solid state physics -- Periodicals; Materials science -- Periodicals; 530.41
• DOI: 10.1088/2515-7639/abd73d
• Languages: English
• ISSNs: 2515-7639

Abstract

Abstract: The partial replacement of Cu by Ag in Cu(In, Ga)Se2 thin-film solar cells is strategically interesting to achieve smooth devices with high conversion efficiencies. Yet, the industrial exploitation requires further understanding of the deposition process and control of the absorber layer properties. In this study, three-stage co-evaporation of (Ag, Cu)(Ga, In)Se2 films with [Ag]/([Ag] + [Cu]) contents up to 0.2 was investigated. Deep crevices and voids, sometimes extending down to the rear contact, were found. They mainly occur for high Ag contents and excessive group-I richness during the second stage of the deposition. The formation of cavities is attributed to the segregation of Ag–Se phases and slow Ag diffusion into the chalcopyrite during the deposition. Another identified challenge is the flattening of the desired bandgap grading which is correlated with the Ag content. Optimized process conditions allow fabrication of smooth (Ag, Cu)(Ga, In)Se2 films in a manufacturing-like inline deposition with cell efficiencies up to 20.5%.