The Effects of Dopant Profiles on the Device Parapmetrs of p-i-n and n-i-p a-Si Solar Cells

Abstract

We have studied the effects of intrinsic layer dopant profiles on the open circuit voltage and fill factor of p-i-n and n-i-p solar cells. Data is presented showing that boron profiling into the i-layer is responsible for the commonly observed difference in open circuit voltage between p-i-n and n-i-p devices. As only a shallow profile is required to produce this effect, it is proposed that the lower V_oc samples are being limited by surface recombination at the p/i interface and that the boron profile reduces this recombination current. The fill factor for devices illuminated through the n⁺ layer is shown to be very sensitive to the depth of a boron profile, yet not so sensitive to the profile concentration. A maximum occurs for a profile penetrating slightly more than half way through the cell. Spectral response data clearly shows a shifting of high collection from the back to the front of the cell.