New materials and new analysis method for high-efficiency a-Si solar cells

The authors present investigations of high-efficiency a-Si solar cells and describe a novel structure for large-area a-Si solar cell submodules. In order to improve the conversion efficiency, B(CH₃)₃ was applied as a new p-type doping gas, which led to a total-area efficiency of 9.60% for a 10 cm*10 cm integrated-type submodule. Furthermore, a novel analysis method, called the current-separated-analysis method, was developed to obtain key factors for high open-circuit voltage. Based on this analysis, microcrystalline SiC films were investigated using an original plasma chemical vapor deposition method, called the controlled-plasma-magnetron method. An open-circuit voltage of 0.98 V was obtained by using p-type microcrystalline SiC. In addition, a through-hole contact structure was developed for large-area solar cells. Using this structure, the active area can be increased and a high-efficiency submodule obtained.