We investigated a double silicon-carbide p-layer structure consisting of a undiluted p-type amorphous silicon-carbide (p-a-SiC:H) window layer and a hydrogen diluted p-a-SiC:H buffer layer to improve a pin-type amorphous silicon based solar cell. Solar cells using a lightly boron-doped (1000 ppm) buffer layer with a high conductivity, low absorption, well-ordered film structure, and slow deposition rate improves the open-circuit voltage (V-oc), short-circuit current density, and fill factor by reducing recombination in the buffer layer and at p/buffer and buffer/i interfaces. It is found that a natural hydrogen treatment generated throughout the buffer layer deposition onto the p-a-SiC:H window layer is an advantage of this double p-layer structure. We achieved a considerable initial conversion efficiency of 11.2% without any back reflector. (C) 2004 American Institute of Physics.