Nanoimprint lithography for solar cell texturisation

The highest efficiency silicon solar cells are fabricated using defined texturing schemes by applying etching masks. However, for an industrial production of solar cells the usage of photolithographic processes to pattern these etching masks is too consumptive. Especially for multicrystalline silicon, there is a huge difference in the quality of the texture realized in high efficiency laboratory scale and maskless industrial scale fabrication. In this work we are describing the topography of a desired texture for solar cell front surfaces. We are investigating UV-nanoimprint lithography (UV-NIL) as a potential technology to substitute photolithography and so to enable the benefits resulting of a defined texture in industrially feasible processes. Besides the reduced process complexity, UV-NIL offers new possibilities in terms of structure shape and resolution of the generated etching mask. As mastering technology for the stamps we need in the UV-NIL, interference lithography is used. The UV-NIL process is conducted using flexible UV-transparent stamps to allow a full wafer process. The following texturisation process is realized via crystal orientation independent plasma etching to tap the full potential of the presented process chain especially for multicrystalline silicon. The textured surfaces are characerised optically using fourier spectroscopy.

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