Open AccessWide Band Gap Cu2SrSnS4 Solar Cells from Oxide Precursors
Author(s) -
Andrea Crovetto,
Rasmus Nielsen,
Eugen Stamate,
Ole Hansen,
Brian Seger,
Ib Chorkendorff,
Peter C. K. Vesborg
Publication year - 2019
Publication title -
acs applied energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.833
H-Index - 36
ISSN - 2574-0962
DOI - 10.1021/acsaem.9b01322
Subject(s) - czts , band gap , materials science , photoluminescence , conduction band , photovoltaics , tandem , optoelectronics , kesterite , solar cell , oxide , electron , nanotechnology , photovoltaic system , metallurgy , physics , electrical engineering , composite material , quantum mechanics , engineering
Recent progress in the efficiency of Cu2ZnSnS4 (CZTS) solar cells has been relatively slow due to severe bulk band tailing issues that have proven difficult to resolve. Band tails in CZTS are caused by defect-related potential fluctuations, as diagnosed by the large shift between the CZTS band gap and its photoluminescence (PL) peak. In this work, we demonstrate that the PL-band gap shift can be decreased roughly by a factor of 5 when Zn is replaced by the heavier cation Sr. The resulting Cu2SrSnS4 compound is of considerable interest for photovoltaics due to its sharp band edges and suitable band gap (1.95-1.98 eV) for a top absorber in tandem cells. Trigonal CSTS thin films are synthesized by sulfurization of strongly Cu-poor cosputtered Cu2SrSnO4 precursors. The first functioning CSTS solar cells are demonstrated, even though the very high conduction band of CSTS implies that the typical CdS/ZnO electron contact of CZTS solar cells must be redesigned to avoid large voltage losses.
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