In-situ diagnostics for preparation of laser crystallized silicon films onglass for solar cells

Polycrystalline silicon thin film solar cells require coarse grained silico n layers on a glass substrate. The preparation starts with a layer of amorp hous silicon some hundred nanometers thick. By laser crystallization it is converted into a seed layer consisting of grains several ten mu m in size. We report on in situ diagnostics by time resolved reflection and transmissi on (TRRT) measurements during the preparation process. Joint diagnostics by different lasers and the comparison with optical and electron micrographs of the resulting films give unique information about the crystallization pr ocesses. Even if different processes occur in hydrogenated or hydrogen free amorphous silicon films during the heating induced by different irradiatio n parameters the results of crystallization are quite similar. (C) 1999 Els evier Science S.A. All rights reserved.