Epitaxy-through-holes process for epitaxy wrap-through solar cells

The Epitaxy Wrap-Through (EpiWT) cell is a rear contact version of the Epitaxial Wafer-Equivalent cell which is a crystalline silicon thin-film solar cell developed at Fraunhofer ISE. The EpiWT concept is similar to an Emitter Wrap-Through cell except that all layers are wrapped through holes instead of only the emitter. The attempt to grow silicon layers epitaxially through small via holes, that is three dimensionally, is a completely new development. We now successfully developed a 3D epitaxy process which provides us with very well suited layers for fabricating EpiWT cells. Besides this epitaxy-through-hole process, this paper focuses mainly on the characterisation of the resultant EpiWT cell structure.