In order to improve the conversion efficiency of amorphous silicon (a-Si:H) alloy p-i-n solar cells, the original p-a-Si:H window layer is substituted by the boron-doped amorphous diamond (a-D:B) films deposited using filtered cathodic vacuum arc technology. The microstructural, optical and electrical properties as functions of the boron concentrations in the films were, respectively, evaluated by an X-ray photoemission spectroscopy, ail ultraviolet-visible spectrometer and a semiconductor parameter analyzer. The photovoltaic parameters of the solar cell modules were also detected as functions of boron concentration. It has been shown that the conductive a-D:B films could be obtained and still remained a wide optical gal). The p-i-n structural amorphous silicon solar cell using the a-D:B window layer increased the conversion efficiency by a roughly 10% relative improvement compared to the conventional amorphous silicon solar cell because of the enhancement of short wavelength response. (C) 2009 Elsevier B.V. All rights reserved.