This process is based on a combination of meltmediated 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 epitaxy (SPE) 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 SPE process by way of a furnace anneal.
Such a combined laser-SPE 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 solid phase crystallization processes (SPC) 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-SPE 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 HIGHEF 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 8 organizations from 4 different member states with 1 associatedcountry.