A low cost kerfless thin crystalline Si solar cell technology

Abstract

The crystalline Si photovoltaic industry has been scaling down the Si wafer thickness in order to reduce costs and potentially attain higher efficiencies by minimizing bulk recombination. However, cell manufacturers are struggling to reduce the wafer thickness below 150μm as there are no economically viable technologies for manufacturing very thin Si wafers and such thin silicon wafers impose stringent handling requirements as wafer breakage and yield loss impact final module cost. We have previously reported a novel kerfless exfoliation technology capable of producing ultra thin 25μm thin flexible mono c-Si foils from thick Si wafers. In this work, we report on scaling the technology to 8-inch diameter wafers. A 25μm thin exfoliated monocrystalline Si solar cell with a front heterojunction emitter and a diffused back surface field structure has been fabricated with a power conversion efficiency of 14.9%. Simulations show that with optimized texturing of the foil and better surface passivation, higher efficiencies (20%) can be attained. We have also fabricated dual heterojunction devices on 25μm thin exfoliated Si, which show high V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> of 680mV. Due to the kerfless exfoliation process and wafer reuse, a final cell cost of $0.30/Wp can be achieved.