Preparation and properties of evaporated CdTe films compared with single crystal CdTe. Progress report No. 4, August 1-October 31, 1981
The hot-wall vacuum evaporation system is nearly complete and the first films are expected in early December. CdTe homojunction cells were theoretically modelled and to some extent tested experimentally using the n-type CdTe film on p-type CdTe crystal homojunction cells previously deposited at Linz. Modelling emphasizes the known importance of surface recombination velocity for such homojunction cells. The n-type layer on the experimental cell was thinned by etching from 5 micrometers to 1.5 micrometers, with a corresponding increase in short-circuit current from 0.1 to 1 mA/cm/sup 2/. This behavior is as theoretically expected; to obtain a short-circuit current of 11 mA/cm/sup 2/, as required for a 10% cell, requires a thickness of about 0.2 micrometers for a surface recombination velocity of 10/sup 6/ cm/sec and other realistic cell parameters. By doping experiments on single crystal CdTe, it has been shown that the hole density does decrease when the P dopant density is decreased below a critical value in CdTe:P crystals, thus eliminating the possibility that the major acceptors in the P-doped crystals were not P impurity. Attempts to heavily dope CdTe with As were less successful, but this may be due to the use of elemental As as the dopant in this case rather than a compound of the dopant. Cs was shown to be an effective dopant of CdTe and resistivities as low as 0.3 ohm-cm corresponding to hole densities in the low 10/sup 17/ cm/sup -3/ range were obtained. An apparent correlation between the low-temperature barrier height associated with a grain boundary in CdTe and the angle of mismatch between the two grains has been observed. Improved capacitance of grain boundary measurements should yield defect densities.
- Research Organization:
- Solar Energy Research Inst. (SERI), Golden, CO (United States)
- DOE Contract Number:
- AC02-77CH00178
- OSTI ID:
- 5627195
- Report Number(s):
- SERI/PR-9330-1-T4; ON: DE82003925
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CADMIUM TELLURIDE SOLAR CELLS
RECOMBINATION
CADMIUM TELLURIDES
CRYSTAL DOPING
GRAIN BOUNDARIES
ARSENIC ADDITIONS
CAPACITANCE
CARRIER DENSITY
CESIUM ADDITIONS
CRYSTAL DEFECTS
ELECTRIC CURRENTS
ETCHING
HOMOJUNCTIONS
MONOCRYSTALS
N-TYPE CONDUCTORS
PHOSPHORUS ADDITIONS
VACUUM EVAPORATION
ALLOYS
ARSENIC ALLOYS
CADMIUM COMPOUNDS
CESIUM ALLOYS
CHALCOGENIDES
CRYSTAL STRUCTURE
CRYSTALS
CURRENTS
DIRECT ENERGY CONVERTERS
ELECTRICAL PROPERTIES
EQUIPMENT
EVAPORATION
JUNCTIONS
MATERIALS
MICROSTRUCTURE
PHASE TRANSFORMATIONS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
SEMICONDUCTOR JUNCTIONS
SEMICONDUCTOR MATERIALS
SOLAR CELLS
SOLAR EQUIPMENT
SURFACE FINISHING
TELLURIDES
TELLURIUM COMPOUNDS
SOLAR
CDTE FILMS
EVAPORATED
SINGLE CRYSTAL
140501* - Solar Energy Conversion- Photovoltaic Conversion