Surface preparation effects on efficient indium-tin-oxide-CdTe and CdS-CdTe heterojunction solar cells
The effects of CdTe surface preparation and subsequent junction formation have been investigated through characterization of ITO/CdTe and CdS/CdTe heterojunction solar cells formed by electron beam evaporation of indium-tin-oxide (ITO) and CdS onto single crystal p-type CdTe. Surfaces investigated include air-cleaved (110) surfaces, bromine-in-methanol etched (110) and (111) surfaces, and teh latter surfaces subjected to a hydrogen heat treatment. Both air-cleaved and hydrogen heat treated surfaces have a stoichiometric Cd to Te ratio. The ITO/CdTe junction formation process involves an air heat treatment, which ahs serious effects on the behavior of junctions formed on these surfaces. Etched surfaces which have a large excesss of Te, are less affected by the junction formation process and result in ITO/CdTe heterojunctions with solar efficiencies of 9% (V/sub s/c = 20 mA/cm/sup 2/). Use of low-doped CdTe results in junctions characterized by considerably larger open-circuit votages (V/sub o/c = 0.81 V) which are attributable to increasing diode factors caused by a shift from interfacial recombination to recombination in the depletion region. Resulting solar efficiencies reach 10.5% which is the highest value reported to date for a genuine CdTe heterojunction, CdS/CdTe heterojunctions show a strong dependence on CdTe surface condition, but less influence on the junction formation process. Solar efficiencies of 7.5% on an etched and heat treated surface are observed. All of these ITO/CdTe and CdS/CdTe heterojunctions have been stable for at least 10 months.
- Research Organization:
- Department of Materials Science and Engineering, Stanford University, Stanford, California 94305
- OSTI ID:
- 6170785
- Journal Information:
- J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 54:5; ISSN JAPIA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
ALCOHOLS
BEAMS
BROMINE
CADMIUM SULFIDE SOLAR CELLS
CADMIUM TELLURIDE SOLAR CELLS
CHALCOGENIDES
CLEAVAGE
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DATA
DIRECT ENERGY CONVERTERS
ELECTRON BEAMS
ELEMENTS
EQUIPMENT
ETCHING
EVAPORATION
EXPERIMENTAL DATA
HALOGENS
HEAT TREATMENTS
HYDROGEN
HYDROXY COMPOUNDS
INDIUM
INFORMATION
LEPTON BEAMS
METALS
METHANOL
MICROSTRUCTURE
MONOCRYSTALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORIENTATION
OXIDES
OXYGEN COMPOUNDS
PARTICLE BEAMS
PHASE TRANSFORMATIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
SOLAR CELLS
SOLAR EQUIPMENT
STOICHIOMETRY
SURFACE FINISHING
TIN COMPOUNDS
TIN OXIDES