Lead by the Energy research Center of the Netherlands (ECN), a consortium of seven European partners and one Chinese university collaborate in a new solar cell research project with the name Silicon-Light. This project has started on January 1 of 2010 and will last for three years. The aim of this project is to enable the fabrication of better and cheaper thin film silicon solar cells on foil. These “solar foils” are extremely well suited for building integrated PV applications.

Silicon is a superb feedstock material for solar cells. To make cells with high efficiencies, though, it is important to make the silicon as pure as possible. This purification is an expensive process, and therefore it is necessary to make the solar cells as thin as possible. In Silicon-Light  methods are being investigated and improved to fabricate thin silicon layers with thickness of about 1/1000 of a millimetre out of a gas phase on foil by means of Plasma Enhanced Chemical Vapour Deposition (PECVD).  The purpose is to make high quality amorphous and micro-crystalline silicon at relatively low process temperatures (typically below 200 ºC), allowing the usage of cheap plastics as substrate foil. To collect all sunlight into only one micrometer of silicon, special structures need to be incorporated in the solar cells which trap the light. In Silicon-Light we investigate methods to create light-scattering textures at the rear side of the cell. For the fabrication of these textures, with structures on nanometre scale, methods from the semiconductor industry like e-beam lithography will be applied. To demonstrate that these textures can be manufactured on large scale, these methods will be combined with large scale production methods which are used in the holographic industry.

Another aim of the project is to develop new TCO layers for thin film silicon solar cells. TCO (Transparent Conductive Oxide) layers are needed to collect the generated current at the front side of the solar cell. Indium Tin Oxide (ITO) is technically a good candidate but the scarceness of Indium requires to investigate alternative materials. Zinc-Oxide is a possible alternative but has certain disadvantages related to its stability in humid environments. In Silicon-Light new TCO materials will be developed that should combine the advantages of ITO with that of ZnO.

The consortium of Silicon-Light consists of eight partners with different backgrounds. Besides ECN as coordinator and solar cell research institute, the following parties participate: EPFL (Switzerland): a top-institute in the field of thin film silicon solar cells; University of Ljubjana specialized in the theory of light-management in solar cells; University of Copenhagen: specialized in electron microscopy for analysis of thin layers; University of Valencia and the JiaoTong University of Shanghai for the fabrication of nanometre scale structures by e-beam lithography; Umicore Thin Film Products AG as manufacturer of materials for thin film solar cells and finally VHF Technologies: a manufacturer of thin film silicon solar cells, as an end user of the project.

The project Silicon-Light is subsidized by the European Commission in the framework of the thematic research programme Energy in FP7.

 

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