Studies on amorphous siliconp‐ndiodes have shown that theplayers are photovoltaically active.Jscof up to 3.4 mA/cm2andVocof 780 mV have been observed. Detailed quantum efficiency measurements were performed as a function of bias voltage,p‐layer thickness, and boron doping. The data fit a simple depletion width model in which all photogenerated carriers created inside the depletion region are collected. An additional ‘‘reverse’’ barrier depletion width is assumed at the interface between the front transparent oxide electrode and theplayer to explain the results. A 10‐nm‐thickplayer typically used inp‐i‐ncells could collect up to 1 mA/cm2if the electric field in theplayer is greater than 105V/cm.