Growth of thin crystalline silicon layers for photovoltaic device use

Abstract

Because of the current interest in thin-layer (5–50 μm) crystalline silicon for photovoltaic (PV) applications, we have grown Si layers on (111) single crystal Si substrates from the metal solvents Ga, Sn, and Cu with a particular emphasis on Cu. A substrate dipping technique was used, and the growth temperature was typically near 950°C. The conditions of growth, morphology, qualitative solvent incorporation characteristics, and electrical properties of the solution-grown layers are presented and discussed. Thin single crystal layers with suitable impurity characteristics for photovoltaic use were obtained, and solar cells with 15% conversion efficiency were fabricated on 5 μm thick layers grown on single crystal Si substrates. This is 97% of the efficiency obtained on substrates without a grown layer, and indicates that the Cu solution growth process does not significantly degrade cell performance.