HIGH-EF

Large grained, low stress multi-crystalline silicon thin film solar cells on glass by a novel combined diode laser and solid phase crystallization process

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 Obiettivo del progetto (Objective)

HIGH-EF will provide the silicon thin film photovoltaic (PV) industry with a unique process allowing for high solar cell efficiencies (potential for >10%) by large, low defective grains and low stress levels in the material at competitive production costs. This process is based on a combination of melt-mediated crystallization of an amorphous silicon (a-Si) seed layer (<500 nm thickness) and epitaxial thickening (to >2 µm) of the seed layer by a solid phase crystallization (SPC) process. Melting the a-Si layer and solidifying large grains (about 100 µm) will be obtained by scanning a beam of a diode laser array. Epitaxial thickening of the large grained seed layer (including a pn-junction) is realized by deposition of doped a-Si atop the seed layer and a subsequent SPC process by way of a furnace anneal. Such a combined laser-SPC process represents a major break-through in silicon thin film photovoltaics on glass as it will substantially enhance the grain size and reduce the defect density and stress levels of multi-crystalline thin layers on glass compared e.g. to standard SPC processes on glass, which provide grains less than 10 µm in diameter with a high density of internal extended defects, which all hamper good solar cell efficiencies. It is, however, essential for the industrial laser-SPC implementation that such a process will not be more expensive than the established pure SPC process. A low cost laser processing will be developed in HIGH-EF using highly efficient laser diodes, combined to form a line focus that allows the crystallization of an entire module (e.g. 1.4 m x 1 m in the production line or 30 cm x 39 cm in the research line) within a single scan. Specific attention has been given to identify each competence needed for the success of the project and to identify the relevant partners forming a balanced, multi-disciplinary consortium gathering 7 organizations from 4 different member states with 1 associated country.

Introduzione (Teaser)

New, laser-enhanced crystallisation processes on glass will offer better solar cell efficiency with low silicon consumption.

Descrizione progetto (Article)

The EU-funded HIGH-EF project set out to provide the silicon thin-film photovoltaic (PV) industry with a unique process allowing for high solar cell efficiencies.

Based on the combination of crystallisation and thickening by a solid phase crystallisation (SPC) process, laser SPC is a major breakthrough in silicon thin-film PV on glass since it greatly increases the grain size and reduces the density of defects and stress levels. Standard SPC processes on glass provide smaller grains with a high density of internal extended defects that hinder good solar cell efficiencies.

It was deemed important, however, that the cost of industrial laser SPC implementation should not be more than the pure SPC process. The HIGH-EF project worked on developing low-cost laser processing using highly efficient laser diodes. The goal was to combine these to form a line focus allowing for the crystallisation of an entire module within a single scan.

Attention was focused on identifying each competence needed for the project's success and to select partners to form a multidisciplinary consortium bringing together seven organisations from four Member States and one associated country. All efforts aimed to advance the technology of multicrystalline thin-film silicon solar-cells through the new laser SPC process.