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HIGH-EFFICIENCY THIN FILM SOLAR CELLS ON UPGRADED METALLURGICAL GRADE SILICON SUBSTRATES.

Objective

STUDY OF THE POTENTIAL OF THE EPITAXIAL GROWTH OF HIGH EFFICIENCY SOLAR CELLS ON UPGRADED METALLURGICAL GRADE SILICON SUBSTRATES.

WE HAVE ALREADY SHOWN IN THE COURSE OF THE LAST YEARS THAT IN POLYCRYSTALLINE SILICON OF METALLURGICAL ORIGIN DEEP LEVEL IMPURITIES COULD BE REMOVED EFFICIENTLY BY A SUITABLY PERFORMED CRYSTALLIZATION AND THAT, THEREFORE, THE ELECTRICAL PROPERTIES OF THIS MATERIAL ARE DOMINATED BY MICROSTRUCTURAL FEATURES AND BY NATIVE IMPURITIES SEGREGATION AT EXTENDED DEFECTS (GRAIN BOUNDARIES AND DISLOCATIONS).
AIM OF THE WORK CARRIED OUT IN THE LAST YEAR WAS TO DEMONSTRATE AN ONE TO ONE CORRESPONDENCE BETWEEN SEGREGATION FEATURES AT GRAIN BOUNDARIES AND ELECTRICAL ACTIVITY.
TO THIS SCOPE, MORPHOLOGICAL AND ELECTRICAL CHARACTERIZATION OF POLYCRYSTALLINE SAMPLE WAS CARRIED OUT, THESE LAST SELECTED FOR THEIR APPROPRIATE OXYGEN TO CARBON RATIOS.
SIMS AND LBIC CHARACTERIZATION WAS FOUND APPROPRIATE FOR LOCAL CHEMICAL AND ELECTRICAL FEATURES DETERMINATION, WHILE A COMPARISON OF THE SECONDARY ELECTRONS MAP WITH THE EBIC MAP OF THE SAME SAMPLE WAS USED TO OBTAIN A MEASURE OF THE PARAMETER TR WHICH IS A MEASURE OF THE AVERAGE RECOMBINATION EFFICIENCY OF A SPECIFIC SAMPLE.
THE EXPERIMENTAL RESULTS SHOW THAT TR VALUES ENTIRELY DPEND ON THE EXCESS OF OXYGEN VS CARBON CONTENT.
IT FITS ALSO QUITE WELL WITH THE DEPENDENCE OF THE DIFFUSION LENGTH OF MINORITY CARRIERS ON THE OXYGEN EXCESS, TAKING A MINIMUM VALUE WHEN LD PEAKS TO ITS MAXIMUM VALUE.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

THE UNIVERSITY OF MILANO
Address
Via Golgi 19
20133 Milano
Italy