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HIGH EFFICIENCY III-V SOLAR CELLS FOR USE WITH FLUORECENT CONCENTRATORS.

Objective

A STACK OF FLUORESCENT PLANAR CONCENTRATORS (FPC) OFFERS THE POSSIBILITY TO DIVIDE PART OF THE SOLAR SPECTRUM INTO DIFFERENT SPECTRAL REGIONS, EACH OF WHICH CAN BE CONVERTED BY SPECTRALLY MATCHED SOLAR CELLS WITH A HIGHER EFFICIENCY THAN THAT OF A SINGLE CELL FOR THE SUM OF THE REGIONS.

PURPOSE OF THE PROJECT IS TO OPTIMIZE THE SYSTEM FPC/III-V SOLAR CELL BY MONTE CARLO SIMULATION, CHARACTERIZE THE GAAS- AND GA1-X ALX AS-SOLAR CELLS TO BE FABRICATED BY THE INTERUNIVERSITY MICROELECTRONICS CENTER (IMEC), LEUVEN AND TO BUILD THE FINAL STACK WHICH SHOULD HAVE AN ELECTRICAL EFFICIENCY OF WELL ABOVE 4%. AT PRESENT DATA ABOUT III-V SOLAR CELLS ARE BEING COLLECTED AND PROCESSED.
High efficiency III-V solar cells can be used with fluorescent concentrators. Fluorescent planar concentrators (FPC) combine the effects of a low level concentrator and a spectrum splitter. The unique feature is the ability to concentrate diffuse light too, thus eliminating the need for tracking, and making low light applications highly attractive. FPCs reduce the solar cell area needed compared to directly exposed generators but, as their overall electrical efficiency is rather poor, they need large areas.
FLUORESCENT CONCENTRATORS CONSIST OF A SHEET OF HIGHLY TRANSPARENT MATERIAL, SEVERAL MM THICK WHICH IS DOPED WITH A FLUORESCENT DYE WHICH ABSORBS PART OF THE SUNLIGHT AND REEMITS IT SHIFTED TO LONGER WAVE LENGTHS - AS FLUORESCENCE. ABOUT 75% OF THE FLUORESCENT LIGHT IS TRAPPED IN THE SHEET BY TOTAL INTERNAL REFLECTION AND GUIDED TO THE EDGES WHERE SOLAR CELLS ARE MOUNTED. A GREAT ADVANTAGE OF FLUORESCENT CONCENTRATORS IS THEIR ABILITY TO CONCENTRATE DIFFUSE LIGHT AS WELL AS DIRECT LIGHT. THEREFORE NO TRACKING OF THE SUN IS REQUIRED. GAAS- AND GA1-XALXAS-SOLAR CELLS ARE ESPECIALLY WELL-SUITED FOR FLUORESCENT CONCENTRATORS, THIER BAND GAPS LIE CLOSER TO THE FLUORESCENT EMISSION THAN THAT OF SILICON, THE BAND GAP OF GA1-XALXAS CAN BE OPTIMIZED WITH RESPECT TO THE FLUORESCENCE BY VARYING THE ALUMINIUM CONTENT AND THE EFFIENCY DEGRADATION WITH INCREASING TEMPERATUR IS LESS PRONOUNCED THAN WITH SILICON.33A STACK OF.33A STACK OF FLUORESCENT PLANAR CONCENTRATORS (FPC) OFFERS THE POSSIBILITY TO DIVIDE PART OF THE SOLAR SPECTRUM INTO DIFFERENT SPECTRAL REGIONS, EACH OF WHICH CAN BE CONVERTED BY SPECTRALLY MATCHED SOLAR CELLS WITH A HIGHER EFFICIENCY THAN THAT OF A SINGLE CELL FOR THE SUM OF THE REGIONS. PURPOSE OF THE PROJECT IS TO OPTIMIZE THE SYSTEM FPC/III-V SOLAR CELL FABRICATED BY THE INTERUNIVERSITY MICROELECTRONICS CENTER (IMEC), LEUVEN, AND TO BUILD THE FINAL STACK WHICH SHOULD HAVE AN ELECTRICAL EFFICIENCY OF WELL ABOVE 4%.

SO FAR NO OPTIMIZED III-V SOLAR CELLS WERE AVAILABLE. WITH GAAS SOLAR CELLS WHICH CISE, MILANO MADE AVAILABLE, A TWO SHEET FPC STACK YIELDED AN OVERALL ELECTRICAL EFFICIENCY OF 4.1% AT AN EFFECTIVE CONCENTRATION RATIO OF 2.7.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG E.V.*
Address
Heidenhofstrasse 2
79110 Freiburg (In Breisgau)
Germany