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ELECTROCHEMICAL STUDY OF CHALCOPYRITE SEMICONDUCTORS

Objective

THE AIM OF THIS RESEARCH WORK IS TO ESTABLISH A CORRELATION BETWEEN THE COMPOSITION OF CHALCOPYRITE SEMICONDUCTORS AND THEIR ELECTRONIC PROPERTIES.
THERE IS THEREFORE A NEED FOR A QUICK SIMPLE TECHNIQUE ABLE TO GIVE COMPOSITION OF THIN LAYER SAMPLES. ELECTROCHEMICAL TECHNIQUES ARE TO GIVE THIS INFORMATION, USING FRACTIONAL OXIDATION OR REDUCTION. FRACTIONAL OXIDATION MEANS THAT THE ELEMENTS CONSTITUTING THE MATERIAL ARE SUCCESSIVELY OXIDISED, GIVING RISE TO SIGNALS PROPORTIONAL TO THEIR CONCENTRATION.

AN ELECTROCHEMICAL TECHNIQUE FOR THE ANALYSIS OF COPPER INDIUM (OR GALLIUM OR INDIUM-GALLIUM) DISELENIDE HAS BEEN SUCCESSFULLY DEVELOPED. THE OBJECTIVE WAS TO PROVIDE A REFERENCE METHOD FOR THE DETERMINATION OF COMPOSITIONS. THE RELATIVE ERROR FOR EACH METAL COMPONENT IS ESTIMATED TO BE EQUAL TO 0.25 0.5% FOR THE METALS AND 0.7% FOR THE SELENIUM. THE TECHNIQUE MAKES USE OF PULSE POLAROGRAPHIC AND AMPEROMETRIC TECHNICS, THE RESULTS MAY BE OBTAINED AFTER ONE OR TWO HOURS, DEPENDING ON THE COMPLEXITY OF THE COMPOSITION AND NEEDS ONLY 2 MG OF MATERIAL (DISSOLVED BY A CHEMICAL OXIDATION). THE INTERESTS ARE TO AVERAGE LOCAL VARIATIONS IN THE SAMPLE COMPOSITION AND TO BE INDEPENDENT OF ITS MORPHOLOGY.
THE SEMICONDUCTING PROPERTIES OF AS EVAPORATED FILMS (BAND GAP, TYPE AND DOPING LEVEL, SPECTRAL RESPONSE, EFFECTIVE DIFFUSION LENGTH) WERE OBTAINED BY USING THE JUNCTION FORMED WITH AN APPROPRIATE ELECTROLYTE (LIQUID JUNCTION). IT HAS BEEN SHOWN THAT COMPOSITIONAL PARAMETERS (DEVIATION FROM MOLE-CULARITY AND DEVIATION FROM STOECHIOMETRY) ALLOW THE CLASSIFICATION OF A SET OF COPPER GALLIUM DISELENIDE FILMS WITH DIFFERENT COMPOSITIONS. THE BEST FILMS FOR PHOTOVOLTAICS WERE SITUATED IN THE MONOPHASIC RANGE WITH A SMALL SE DEFICIENCY. COPPER INDIUM DISELENIDE BILAYERS OF STANDARD COMPOSITION EXHIBIT GOOD PHOTOELECTROCHEMICAL CHARACTERISTICS (HIGH QUANTUM EFFICIENCIES~~0.7-0.8) IN AGREEMENT WITH THE RESULTS OBTAINED IN SOLID STATE CELLS. IN SOME CASES STRONG CHEMICAL INTERACTIONS WITH THE ELECTROLYTE HAVE BEEN OBSERVED WHICH COULD BE FURTHER USED FOR IMPROVING THE LAYERS.
THE FILMS WERE PREPARED AT THE INSTITUT FUER PHYSIKALISCHE ELEKTRONIK, STUTTGART.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Address
Rue Pierre Et Marie Curie 11
75231 Paris
France