High Photovoltage Generation at Minority-Carrier Controlled n-Si/p-CuI Heterojunction with Morphologically Soft CuI

Solar cells with a structure of p−n heterojunction, “ITO/p-CuI/n-Si” (ITO = indium tin oxide), were fabricated by depositing p-CuI on hydrogen (H)-terminated or methyl (CH 3)-terminated single-crystal n-Si (111) followed by the sputter deposition of ITO or by the press-contact of commercial conductive oxide glass with p-CuI. The solar cells generated very high open-circuit photovoltages ( V oc), reaching 0.617 V without surface texturing and back surface field treatments. Experiments have shown that a morphologically soft property of p-CuI as well as a low density of surface states at H-terminated or CH 3-terminated n-Si (111) is responsible for the generation of high V oc. Theoretical investigation has also shown that the p-CuI/n-Si contact forms an ideal minority-carrier controlled junction suitable for the generation of high V oc.