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Mono-chess : concepts for high efficiency solar cells

Objective

The overall target of the project is to obtain efficiencies as high as possible by reduction of the mono-crystalline silicon cell thickness. Efficiencies of 20% at 1 sun and 25% for mono-crystalline concentrator cells (under direct beam concentrated light or located into a cavity at 30 W/cm2) are the target figures of MONO-CHESS.
Research is being carried out in order to obtain efficiencies as high as possible by reducing the monocrystalline silicon cell thickness. Efficiencies of 20% at 1 sun and 25% for monocrystalline concentrator cells (under direct beam concentrated light or located into a cavity at 30 W cm{2}) are the target figures of MONO-CHESS. To obtain such cell efficiencies it will be necessary not only to reduce the thickness of the cells in order to increase the open circuit voltage, but also to preserve a high level of light absorption providing optical confinement of the photons.

The following tasks were accomplished:
optimization of textured surfaces and new cell technologies and devices for light confinement;
process development involving techniques for the reduction of recombination and series resistance;
modelling to assess the best structures and the process efforts that must be done first;
measurement of the bonding and cooling of the cells, (in measurements up to 500 suns), spectral response at high injection level and methods of extraction of parameters of the cells;
cell processing which involved combining the preceding successful techniques to obtain high efficiency cells.

These results have achieved an efficiency of 19 to 20% (1 sun) and 24% concentration.
To obtain the mentioned cell efficiencies it will be necessary not only to reduce the thickness of the cells in order to increase the open circuit voltage, but also to preserve a high level of light absorption providing optical confinement of the photons.

According with the above goals, the following tasks must be accomplished as a whole, by the partners:

TASK 1)

OPTICS : Assessment to optimize textured surfaces and new cell technologies and devices for light confinement.
Sub-tasks: 1.1 optical design of cells, 1.2 Texturing development, 1.3 ARC optimization, 1.4 Direct wafer bonding

TASK 2)

PROCESS DEVELOPMENT Includes techniques for the reduction of recombination and series resistance.
Sub-tasks: 2.1 Thinning process development, 2.2 Self-aligned process, 2.3 Surface passivation, 2.4 Reduction of emitter recombination (low Jo)

TASK 3)

MODELLING: To assess the best structures and the process efforts that must be done first.
Sub-tasks: 3.1 Modelling emitter recombination/ structure of cells, 3.2 Modelling base type and doping, 3.3 Series resistance limitations

TASK 4)

MEASUREMENT: It includes the bonding and cooling of the cells, in measurements up to 500 suns, spectral response at high injection level and methods of extraction of parameters of the cells.
Sub-tasks: 4.1 Contact-less measurement and parameter extraction, 4.2 Bonding thin cells to substrata, 4.3 Electrical characterization in wide temperature range under concentrated light

TASK 5)

CELL PROCESSING (FINAL TASK): Combining the preceding successful techniques to obtain high efficiency cells.
Sub-tasks: 5.1 Cell processing at UPM, 5.2 Cell processing at IMEC, 5.3 Cell processing at UCL, 5.4 High efficiency low-cost solar cell processing (Final task)

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSIDAD POLITECNICA DE MADRID
Address
Av. Ramiro De Maeztu 7 S/n
28040 Madrid
Spain

Participants (3)

INTERUNIVERSITAIR MIKRO-ELEKTRONICA CENTRUM VZW
Belgium
Address
75,Kapeldreef 75
3001 Heverlee
UNIVERSITE CATHOLIQUE DE LOUVAIN
Belgium
Address
Place De L'universite 1
Louvain-la-neuve
Université d'Aix-Marseille III (Université de Droit d'Économie et des Sciences)
France
Address
3 Avenue Robert Schuman
13628 Aix-en-provence