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

Objective

THE AIM OF THIS RESEARCH PROJECT IS TO IMPROVE THE EFFICIENCY OF CHEAP POLYCRYSTALLINE SOLAR CELLS MADE BY THE INTEGRAL SCREENPRINTING TECHNIQUE IN EPITAXIAL LAYERS ON UMG-SI-SUBSTRATES.

ONE POSSIBLE STRATEGY TO FABRICATE CHEAP SOLAR CELLS IS VIA THE INTEGRAL SCREEN PRINTING TECHNIQUE IN VERY PURE EPITAXIAL SI-LAYERS ON UMG-SI-SUBSTRATES. VARIOUS SUBSTRATES HAVE BEEN TESTED, SUCH AS POLY- AND MONOCRYSTALLINE WAFERS CZ PULLED FROM (U)MG-SI, AND WAFERS CASTED FROM VARIOUS QUALITIES OF (U)MG-SI BY THE SILSO, HEM (CNRS, PARIS), POLYX (LAB. DE MARCOUSSIS) AND DS (PRAGMA, ROME) TECHNIQUES. FROM ALL THESE, THE HEM AND POLYX AND, PROBABLY, THE DS-WAFERS TOO PROVE TO BE THE BEST CANDIDATES FOR EPI-SOLAR CELL SUBSTRATES. EFFICIENCIES ABOVE 10% ARE READILY OBTAINABLE AS IS INDICATED IN THE TABLE, AND THIS WITH A NOT COMPLETELY OPTIMISED EPI-LAYER DEPOSITION AND SCREEN PRINTING TECHNIQUE. A HIGH TEMPERATURE TREATMENT IN A H2-ENVIRONMENT ON MG-SI SILSO-SUBSTRATES CAN INCREASE THE JSC CONSIDERABLY, WHICH IS PROBABLY DUE TO THE OUTDIFFUSION OF IMPURITIES CONTAINED IN THE GRAINS AS WELL AS IN PRECIPITATES. FOR CELLS MADE IN HEAVILY B-DOPED MONOCRYSTALLINE WAFERS WITHOUT EPI-LAYER THE JSC-INCREASE IS A FUNCTION OF TREATMENT TIME, WHILE THE COVERAGE OF THE WAFER WITH AN EPI-LAYER MASKS ANY EFFECT OF THE HIGH TEMPERATURE TREATMENT AS COULD BE EXPECTED. ON UMG-POLYCRYSTALLINE WAFERS WITH EPI-LAYER ON THE OTHER HAND, THE BENIFICIAL INFLUENCE OF THIS TREATMENT IS STILL NOTICEABLE, WHICH SEEMS TO INDICATE THAT THERE MUST BE SOME FAST DIFFUSING IMPURITY, CONTAINED PROBABLY IN CARBIDE PRECIPITATES AND NOT COMPLETELY DRIVEN OUT BY THE OUTDIFFUSION TREATMENT. AN OPTIMIZATION OF THE EPI-LAYER RESISTIVITY ON CZ-PULLED UMG-SI SUBSTRATES INDICATES AN OPTIMAL VALUE OF ABOUT 3 OHM CM.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

INTERUNIVERSITAIR MIKRO-ELEKTRONICA CENTRUM VZW
Address
75,Kapeldreef 75
3001 Heverlee
Belgium