The silicon on dust substrate path to make solar cells directly from a gaseous feedstock

Abstract

In this paper, we present a silicon on dust substrate (SDS) process, a new method for the growth of silicon ribbons. As a demonstration of the concept, we also present results on solar cells made of these new silicon ribbons. SDS ribbons were obtained directly from a gaseous feedstock by a fast CVD step using silane. The resulting self-supported intrinsic ribbons were microcrystalline and porous. To make these ribbon films suitable for photovoltaic applications, a novel recrystallization with an in situ doping step was developed. To this purpose, the ribbons were sprayed with boric acid and then recrystallized by float zone melting. Simple solar cells were prepared by employing: aluminium back contacts, Ti/Pd/Ag front grid contacts, with no anti-reflective coating, doping optimization, passivation or gettering. The 1-sun I–V characteristics of the cells were: Voc ∼ 530 mV and Jsc ∼ 24 mA cm−2. The minority carrier diffusion length obtained from a spectral response at long wavelengths gave values of Ln ∼ 70 µm.