Effects of Hydrogen Passivation for Spherical Silicon Solar Cells Fabricated by Dropping Method

Abstract

The effects of hydrogen passivation on spherical Si solar cells are investigated. The spherical Si solar cells fabricated from Si spheres produced by a dropping method are multicrystalline Si with dislocations and grain boundaries. In order to inactivate the defects, H-passivation with RF plasma was performed. The short-circuit current density and the open-circuit voltage of spherical Si solar cells increased after H-passivation, consequently, the conversion efficiency was enhanced. Current–voltage characteristics and external quantum efficiency indicated the bulk passivation effect of recombination centers. Moreover, the minority carrier diffusion length (Ln) of the solar cell was estimated by the surface photovoltage method. Ln increased from 14.6 to 30.5 µm upon H-passivation. Laser-beam-induced current (LBIC) analysis indicated that the crystal defects such as dislocations and grain boundaries were made electrically inactive by H-passivation.