Recrystallized silicon thin film structures for solar cells

Two steps of the technological sequence for the realization of crystalline silicon thin film solar cells are described: in a low pressure chemical vapour deposition-reactor (LPCVD) micro-grained silicon layers of 20-40 mym thickness have been deposited from chlorosilanes. The substrates used for fundamental experiments were either mono- or polycrystalline silicon with a patterned oxide layer on top. Subsequently those microcrystalline layers were recrystallized by a surface melting process using a special optical heating system which has been developed for this purpose. During solidification a substantial grain growth was observed leading to grain diameters in the millimeter range. This was due to a special seeding technique. Applying this technique, also low-quality low-cost substrates are expected to be suitable.