Polycrystalline Solar Cells on Metallurgical-Grade Silicon Substrates

Abstract

Thin-film solar cells are fabricated by chemical vapor deposition using SiH2Cl2 on polycrystalline wafers pulled from metallurgical-grade silicon. An AMI conversion efficiency of 7.3% is obtained with a cell configuration of a 25 µm thick p-type active layer and a 0.5 µm thick n+ -type surface layer for a relatively large area of 8.3 cm2. Photocurrent distribution measurements reveal that the grain boundary effect is of minor importance. Higher efficiency is attainable with the same structure in cases where the photocarrier diffusion length in the active layer is improved from the obtained value, 18µm, to a level conventional in an epitaxial layer on single crystals.