Investigation of CdZnTe for Thin-Film Tandem Solar Cell Applications: Preprint
Modeling of two-junction tandem devices shows that for optimal device performance, the bandgap of the top cell should be around 1.6-1.8 eV. CdZnTe alloys can be tailored to yield bandgaps in the desired range. In this study, we considered were used to fabricate these films, using close-spaced sublimation (CSS) and radio-frequency sputtering (RFS) techniques. In the first approach, we used mixed powders of CdTe and ZnTe as the source for film deposition by CSS. Even for the ZnTe/CdTe (95:5 ratio) source material, the deposited films were entirely CdTe due to higher vapor pressure of CdTe. In the second approach, we used pre-alloyed CdZnTe powders (CERAC, Inc.) as the source. Due to the lower sticking coefficient of Zn, even for the source composition of 75% Zn, these films contained very low quantities of Zn (~5%). We tried unsuccessfully to increase the Zn content in the films by confining Zn vapor by enclosing the region between the source and substrate, reducing the substrate temperature to 400C, and adjusting the source/substance distance. Finally, we used thin-film couples consisting of 300-nm-thick CdTe deposited by CSS and 300-nm-thick ZnTe deposited by RFS; the samples were then heat-treated in cadmium chloride vapor. Compositional analysis of the samples showed extensive interdiffusion of Cd and Zn for the annealed samples. We will present the data on the various stack configurations of CdTe and ZnTe, the effect of different post-deposition anneals, the effect of oxygen on the interdiffusion and alloy formation and its possible correlation to the device performance degradation.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 15004063
- Report Number(s):
- NREL/CP-520-33965; TRN: US201015%%299
- Resource Relation:
- Journal Volume: 763; Conference: Prepared for the 2003 Materials Research Society Spring Meeting, 21-25 April 2003, San Francisco, California
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tandem thin-film solar cell using Cd/sub y/Zn/sub 1-y/Te as the wide bandgap component. Annual subcontract report, 1 April 1985-1 April 1986
CdZnTe as a wide-band-gap absorber for a tandem, thin-film solar cell: Final subcontract report, 1 April 1986-31 August 1987
Related Subjects
36 MATERIALS SCIENCE
ALLOYS
CADMIUM CHLORIDES
DEPOSITION
OXYGEN
PERFORMANCE
SIMULATION
SOLAR CELLS
SPUTTERING
SUBLIMATION
SUBSTRATES
VAPOR PRESSURE
PV
CDZNTE
TANDEM DEVICE
BANDGAP
CLOSE-SPACED SUBLIMATION (CSS)
RADIO-FREQUENCY SPUTTERING (RFS)
THIN-FILM
COUPLE
POST-DEPOSITION ANNEAL
INTERDIFFUSION
ATOMIC FORCE MICROSCOPY
X-RAY DIFFRACTION (XRD)
AUGER ELECTRON SPECTROSCOPY (AES)
SECONDARY ION MASS SPECTROMETRY (SIMS)
Solar Energy - Photovoltaics