Silicon thin film solar cell concepts are considered to play an important role in future if the efficiency can be improved to 10 % and more. Specific development projects are focused on the crystallization of a thin silicon layer which is used as a seed to grow 1.5-2.0 µm thick silicon with a polycrystalline structure. The concept is to prepare a thin 50 nm crystalline seed layer and epitactically grow the absorber layer on this seed layer. The absorber layer either is heated in a furnace or by an additional laser process (e.g. 808 nm laser diode heating). The 515 nm pulsed JenLas^® ASAMA operated with VOLCANO^® and LAVA^® Laser Optics allows to crystallize thin silicon layers in a “cold” process without damaging the glass substrate.

Further continuous wave (cw) laser light is applied to generate a crystalline film of very high quality with large grains. The 532 nm LAVA^® CW Laser Optics provides the beam parameters needed for this process. However, special glass properties are needed to compensate potential thermally induced mechanical stress. Typically the Si-film is processed at 100-150 kW/cm² applying high scanning speed.

The efficiency of crystalline cells based on wafers depends strongly on the rate of charge extraction and on low-ohmic contacts. VOLCANO^® laser optics technology operated with the 515 nm JenLas^® ASAMA laser allows easily to concentrate laser light to selective areas on the wafers (selective laser doping). Low resistance contact areas are achieved while optimizing the pn junction with low dopant concentrations for efficient charge carrier generation by the sunlight. A specially designed beam splitter allows simultaneous processing of a large number of contact fingers.