Large-grained polycrystalline silicon on glass for thin-film solar cells

We have investigated the formation of large-grained polycrystalline silicon (poly-Si) films on glass for thin-film solar cells using the ‘seed layer concept’ which is based on the epitaxial thickening of a thin large-grained poly-Si template (seed layer). Due to the glass substrate all process steps are limited to a temperature of about 600 °C. The aluminium-induced layer exchange (ALILE) process based on the aluminium-induced crystallisation (AIC) of amorphous Si has been used to prepare p+-type seed layers featuring large grains and a high preferential (100) orientation of the surface. The seed layers have been thickened by electron cyclotron resonance chemical vapour deposition (ECRCVD) to form the p-type absorber of the solar cell. First poly-Si thin-film solar cell structures have been prepared by deposition of an n+-type a-Si : H emitter. So far an open circuit voltage of 284 mV has been reached without any additional treatments like defect annealing and defect passivation.