Open AccessChallenges in the deposition of (Ag,Cu)(In,Ga)Se2 absorber layers for thin-film solar cells
Author(s) -
Stephanie Essig,
Stefan Paetel,
Theresa Magorian Friedlmeier,
Michael Powalla
Publication year - 2021
Publication title -
jphys materials
Language(s) - English
Resource type - Journals
ISSN - 2515-7639
DOI - 10.1088/2515-7639/abd73d
Subject(s) - chalcopyrite , deposition (geology) , materials science , solar cell , fabrication , thin film , band gap , copper indium gallium selenide solar cells , layer (electronics) , thin film solar cell , flattening , chemical engineering , evaporation , metallurgy , nanotechnology , optoelectronics , copper , composite material , geology , medicine , paleontology , alternative medicine , pathology , sediment , engineering , physics , thermodynamics
The partial replacement of Cu by Ag in Cu(In,Ga)Se 2 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)Se 2 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)Se 2 films in a manufacturing-like inline deposition with cell efficiencies up to 20.5%.