Boron-doped hydrogenated microcrystalline silicon oxide (μc-SiOx:H) for application in thin-film silicon solar cells

Abstract

We report on the development of p-type μc-SiOx:H material, in particular the relationship between the deposition parameters and the material properties like band gap, electrical conductivity, and crystalline volume fraction. The material was deposited from gas mixtures of silane, carbon dioxide and hydrogen by RF-PECVD. The gas flows were varied systematically to evaluate their influence on the material properties. An increase of the oxygen content in the material disturbs the crystalline growth. This can be counteracted by appropriate hydrogen dilutions. Materials with a combination of reasonably high conductivity of 4×10−6 S/cm at a high optical band gap E04 of 2.56 eV and a refractive index of 1.95 are obtained. Applied in single junction μc-Si:H pin solar cells the improved properties of the μc-SiOx:H p-layers are reflected in higher quantum efficiency in the short wavelength range by 10% compare to cells without adding CO2 during p-layer deposition.