Improved photovoltaic properties of amorphous silicon thin-film solar cells with an un-doped silicon oxide layer

Abstract

This paper proposes the use of undoped hydrogenated microcrystalline silicon oxide (μc-SiOx:H) deposited on the n-μc-Si:H layer of amorphous silicon single-junction superstrate configuration thin-film solar cells produced through 40MHz very high frequency plasma-enhanced chemical vapor deposition. Raman spectroscopy and optoelectronic analyses of the undoped μc-SiOx:H thin film revealed that adding a small amount of oxygen into a μc-network results in a low optical absorption, wide band gap, high optical band gap E04, high refractive index, reasonable conductivity, and crystalline volume fraction, which are advantageous properties in solar cells. Compared with a standard cell, the current density–voltage (J–V) characteristics of the cell with an undoped μc-SiOx:H/n-μc-Si:H structure showed an enhancement in short-circuit current density Jsc from 13.32 to 13.60mA/cm2, and in conversion efficiency from 8.53% to 8.61%. The increased Jsc mechanism can be attributed to an improved light-trapping capability in the long wavelength range between 510 and 660nm, as demonstrated by the external quantum efficiency.