TY - JOUR
T1 - Polycrystalline CuGaSe2 thin film growth and photovoltaic devices fabricated on alkali-free and alkali-containing substrates
AU - Ishizuka, Shogo
AU - Fons, Paul J.
N1 - Funding Information:
The authors would like to thank M. Iioka, H. Higuchi, S. Takaesu, and H. Takahashi for their help with the experiments and technical support. This work was supported by JSPS KAKENHI grant number 19K05282 and also supported in part by NEDO .
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2020/2/15
Y1 - 2020/2/15
N2 - Polycrystalline thin films of ternary CuGaSe2 (CGS), which are one of the potential materials for wide-gap top cells in tandem structure photovoltaic devices, are grown on alkali-free and alkali-containing substrates. The effects of alkali-metals on CGS film morphology, grain size, and photovoltaic device properties are studied. High temperature (>600 °C) growth of CGS films is also investigated with a focus upon variations in alkali-metal distribution profiles in CGS films and the formation of a surface Cu-deficient layer (CDL), which plays an important role in p-n junction formation. The use of a high growth temperature is effective in realizing large grain sizes due to enhanced elemental migration during growth, whereas the formation of a surface CDL is diminished and the alkali-distribution profiles in CGS films are modified resulting in a decrease in carrier density. It is suggested that large CGS grain sizes contribute to obtaining high photocurrent values, but coping with modifications in surface/interface and carrier density with alkali-metals is important to enhance overall photovoltaic performance.
AB - Polycrystalline thin films of ternary CuGaSe2 (CGS), which are one of the potential materials for wide-gap top cells in tandem structure photovoltaic devices, are grown on alkali-free and alkali-containing substrates. The effects of alkali-metals on CGS film morphology, grain size, and photovoltaic device properties are studied. High temperature (>600 °C) growth of CGS films is also investigated with a focus upon variations in alkali-metal distribution profiles in CGS films and the formation of a surface Cu-deficient layer (CDL), which plays an important role in p-n junction formation. The use of a high growth temperature is effective in realizing large grain sizes due to enhanced elemental migration during growth, whereas the formation of a surface CDL is diminished and the alkali-distribution profiles in CGS films are modified resulting in a decrease in carrier density. It is suggested that large CGS grain sizes contribute to obtaining high photocurrent values, but coping with modifications in surface/interface and carrier density with alkali-metals is important to enhance overall photovoltaic performance.
KW - A1. Doping
KW - A3. Physical vapor deposition processes
KW - A3. Polycrystalline deposition
KW - B1. Gallium compounds
KW - B3. Solar cells
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U2 - 10.1016/j.jcrysgro.2019.125407
DO - 10.1016/j.jcrysgro.2019.125407
M3 - Article
AN - SCOPUS:85076018007
SN - 0022-0248
VL - 532
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
M1 - 125407
ER -
