Degradation Analysis of Blue Phosphorescent Organic Light Emitting Diode by Impedance Spectroscopy and Transient Electroluminescence Spectroscopy. - Toshinari Ogiwara; Jun-ichi Takahashi; Hitoshi Kuma; Yuichiro Kawamura; Toshihiro Iwakuma; Chishio Hosokawa (IEICE Trans. Electron., 2009)