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Potential of CuS cap to prevent decomposition of Cu 2 ZnSnS 4 during annealing
Author(s) -
Larsen Jes K.,
Scragg Jonathan J. S.,
Frisk Christopher,
Ren Yi,
PlatzerBjörkman Charlotte
Publication year - 2015
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201532420
Subject(s) - czts , annealing (glass) , materials science , thin film , thermal decomposition , chemical process of decomposition , chemical engineering , decomposition , metallurgy , nanotechnology , chemistry , organic chemistry , engineering
One of the challenges associated with processing of Cu 2 ZnSnS 4 (CZTS) is the thermal decomposition reaction that causes loss of S and SnS from the absorber surface. To reduce the decomposition a sufficiently high SnS and S partial pressure must be supplied during annealing. The absorber surface can alternatively be protected with a thin cap. Aiming to obtain a more flexible process, CZTS precursors were capped with a thin CuS layer before annealing. The cap was subsequently removed with a KCN etch before device finishing. It was found that the cap coverage decreased during annealing, exposing a part of the absorber surface. At the same time, the initially Cu poor absorber took up Cu from the cap, ending up with a stoichiometric Cu content. Devices made from capped precursors or precursors annealed without sulfur had poor device characteristics. An increased doping density of almost one order of magnitude could be the reason for the very poor performance. CuS is therefore not a suitable cap material for CZTS. Other cap materials could be investigated to protect the CZTS absorber surface during annealing. A thin CuS cap is deposited on CZTS to prevent surface decomposition during annealing.