Mitsuru Imaizumi is a senior research engineer at JAXA Tsukuba Space Center. He earned his Ph.D. in Materials Science from Toyota Technological Institute in 1999, and his professor was Dr. Masafumi Yamaguchi. He has been in charge of research and development of space solar cells and panels for more than twenty years. Before joining JAXA, he worked for a steel company but was doing MOCVD growth of III-V materials. Owing to the experience, he is currently dealing with III-V muti-junction space solar cells. Recent topic of his research is combing InGaP/GaAs dual-junction cell and CuInGaSe cell with mechanical stack technology to realize never radiation-degrading high-efficiency solar cell.