Investigation of the crystalline and electrical qualities of EPR photovoltaic silicon flat plates

Abstract

The EPR polysilicon ribbons are obtained from 3.5–5N purity grade silicon powder melting. Being assigned to the photocell manufacture we study the texture by X-ray diffraction, ECP (Electron Channeling Pattern) and TEM (Transmission Electron Microscopy) to reveal the crystal orientations of the grains and prove the possible existence of specific orientations adapted to the best photovoltaic conversion efficiency such as on (331), (110), (111). Moreover, we listed the possibility to reduce the (111) orientation with a monocrystalline seed. It appears that the crystal growth is essentially anisotropic and that only the orientation of the grain and then of (331) planes parallel to the ribbon surface may be considered as dominant at last. The crystalline seed is acting only at the crystalline start. The electrical characterizations were executed essentially by EBIC (Electron Beam Induced Current) and LBIC (Laser Beam Induced Current) methods. Two interface types were observed: one parallel and constitued by ∑3 and ∑9 twins, show low electrical activity, the other curved with no defined index and higher electrical activity.