1. Tsukuba Research Center for Interdisciplinary Materials Science (TIMS); Graduate School of Pure and Applied Sciences; University of Tsukuba; Tsukuba 305-8573 Japan
2. Organic Thin-Film Solar Cells Group; Photovoltaic Materials Unit; National Institute for Materials Science (NIMS); Tsukuba Ibaraki 305-0047 Japan
3. Graduate School of Science and Engineering for Research; University of Toyama; 3190 Gofuku Toyama 930-8555 Japan