Solar Cell Processing of Foil Produced by Epoxy-induced Spalling of Silicon

AbstractTo push silicon solar cells up to their theoretical limit and, in the meantime, minimize the amount of active material employed, many researchers have proposed to fabricate silicon solar cells starting from substrates of 100μm or below. A considerable number of methods have been proposed to overcome the limitations of the standard sawing technique but, all of them present some drawbacks. One of these methods, the Slim-cut method, exploits the stress-induced by the deposition of a layer on top of a thick silicon substrate to separate a thin silicon foil. This process however did not solve the issues linked to the processing of free-standing foils.In this work we present a flow to process the Slim-cut foils into solar cells by minimizing the number of process steps performed on free-standing foils to just one step. The possibility to tune the thickness of the obtained silicon foil is investigated both by analytical calculations and experimental results. Moreover, a solution to remove the stress-inducing layer compatible with the flow is reported and lifetime measurements of samples bonded on glass demonstrate that the quality of the samples is high enough for the fabrication of solar cells