Influence of different sulfur to selenium ratios on the structural and electronic properties of Cu(In,Ga)(S,Se){sub 2} thin films and solar cells formed by the stacked elemental layer process
- Robert Bosch GmbH, Corporate Research and Advance Engineering, Advanced Functional Materials and Microsystems, D-70839 Gerlingen (Germany)
- Bosch Solar CISTech GmbH, D-14772 Brandenburg (Germany)
In this study, we investigate the effect of different elemental selenium to elemental sulfur ratios on the chalcopyrite phase formation in Cu(In,Ga)(S,Se){sub 2} thin films. The films are formed by the stacked elemental layer process. The structural and electronic properties of the thin films and solar cells are analyzed by means of scanning electron microscopy, glow discharge optical emission spectrometry, X-ray diffraction, X-ray fluorescence, Raman spectroscopy, spectral photoluminescence as well as current-voltage, and quantum efficiency measurements. The influence of different S/(S+Se) ratios on the anion incorporation and on the Ga/In distribution is investigated. We find a homogenous sulfur concentration profile inside the film from the top surface to the bottom. External quantum efficiency measurements show that the band edge of the solar cell device is shifted to shorter wavelength, which enhances the open-circuit voltages. The relative increase of the open-circuit voltage with S/(S+Se) ratio is lower than expected from the band gap energy trend, which is attributed to the presence of S-induced defects. We also observe a linear decrease of the short-circuit current density with increasing S/(S+Se) ratio which can be explained by a reduced absorption. Above a critical S/(S+Se) ratio of around 0.61, the fill factor drops drastically, which is accompanied by a strong series resistance increase which may be attributed to changes in the back contact or p-n junction properties.
- OSTI ID:
- 22308217
- Journal Information:
- Journal of Applied Physics, Vol. 116, Issue 17; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABSORPTION
CONCENTRATION RATIO
COPPER COMPOUNDS
EMISSION SPECTROSCOPY
FILL FACTORS
FLUORESCENCE
GALLIUM COMPOUNDS
INDIUM COMPOUNDS
PHOTOLUMINESCENCE
P-N JUNCTIONS
QUANTUM EFFICIENCY
RAMAN SPECTROSCOPY
SCANNING ELECTRON MICROSCOPY
SELENIUM COMPOUNDS
SOLAR CELLS
SULFUR COMPOUNDS
THIN FILMS
X RADIATION
X-RAY DIFFRACTION