Performance of n +-p-p + silicon solar cells fabricated through masked ion implantation

Abstract

This work presents the main features of n +-p-p + single-crystalline silicon solar cells whose front junctions were front formed by ion implantation of phosphorus ( 31P +) into p-wafers through a thermally-grown silicon dioxide (SiO 2) mask of variable thickness. The dependence of electro-optical characteristics (peak responsivity wavelength γ s, spectral bandwidth, short-circuit current density J sc , open-circuit voltage V oc , conversion efficiency) on implant parameters (energy, dose, oxide thickness) are discussed in detail. An important result of this research is the increase in J rmsc for fabricated n +-p-p + cells up to 35 mA cm −2 under AM 1 conditions. The best cells fabricated industrially had conversion efficiencies and fill factors of up to 14.3% and 76.8% respectively. The low-energy implanted cells possessed a wideband relative spectral response and γ s was shifted to the visible portion of the spectrum. Detailed explanations of anomalous experimental results and design guidelines for masked ion-implanted silicon n +-p-p + solar cells are also provided. The results obtained show clearly that the desired benefits can be achieved by introducing masked ion implantation into the fabrication of photovoltaic devices.