Duennschichtsolarzellen auf der Basis elektronenstrahlrekristallisierter und durch Fluessigphasenepitaxie verstaerkter Siliziumschichten auf Graphitsubstraten. Teilvorhaben: Hochratenabscheidung und Elektronenstrahlrekristallisierung von solarzellentauglichen Siliziumschichten auf Graphitsubstraten Abschlussbericht

A high rate low temperature PECVD process for deposition of silicon films from trichlorosilane with deposition rates up to 700 nm min"-"1 has been developed. The deposited films are of amorphous or nanocrystalline structure and have a small chlorine content. The electron beam recrystallization of these films is still to be improved with respect to complete surface wetting; yet the feasibility on principle has been shown. The electron beam recrystallization has been extensively examined and developed. The evaluation of the electron beam profile as well as adjusting possibilities have been improved decisively. The whole concept is designed to operate at high throughput. It has been shown that the formation of silicon carbide during recrystallization plays an important role. The parameter during recrystallization can reproducibly be chosen in such a manner that the formation of silicon carbide and the surface condition can be controlled. The so produced silicon seed layers entirely fulfill the requirements for a photovoltaic use with regard to grain size and structure as well as electrical properties. A method for homogeneous doping of the silicon layers by soaking the graphite substrates in a doping solution prior to deposition has been developed. The intensity of doping is controlled by the concentration of the doping solution and the recrystallization parameter. For thickening of the recrystallized films liquid phase epitaxy and vapour phase epitaxy have been studied. It has been shown that growth is disturbed or impeded by silicon carbide and so has to be removed by the help of plasma etching prior to epitaxy. During growth by means of liquid phase epitaxy an island effect occurred. On the other hand with the help of vapour phase epitaxy from silane the deposition of closed layers succeeded; these layers meet the requirements to be processed to thin film solar cells. The generationof cells by using different methods to prepare the pn-junctions have been examined. Diffusion of the emitter from a spinned-on phosphorous glas showed good results. The realization principle of thin film solar cells by the pursued concept, however, has been demonstrated. (orig.)SIGLEAvailable from TIB Hannover: F99B1063+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman