Characterization of boron doped μc-SiC/c-Si heterojunction solar cells

Abstract

The carrier transport mechanisms and interface physics of boron doped microcrystalline silicon carbide (μc-SiC)/crystalline silicon (c-Si) heterostructures have been studied. The sample structure is p-type μc-SiC/c-Si with the window side electrode. A series of systematic measurements on junction characteristics and photovoltaic properties of the heterojunction solar cells are performed. The results of analysis show that an abrupt heterojunction model and a multi-tunneling capture-emission transport mechanism are found to be valid as evidenced by I = I 0exp(AV) relationships where A is a temperature-independent constant. It has been found out that the direct deposition of μc-SiC:H on the c-Si cause the poor junction properties, probably due to high power plasma bombardments, as evidenced by fairly high shunt currents and poor fill factors. A substantial improvement of the junction quality has been achieved by a low power plasma deposition of less than 50 Å thick a-SiC:H as a buffer layer and an AM1 efficiency more than 13.5% solar cell have been fabricated utilizing a low cost polysilicon and a plasma deposited very thin μc-SiC:H. We also discuss the photo-induced degradation in μc-SiC:H thin films and its effects on the devices.