Recoverable degradation and internal field forming process accompanied by the orientation of dipoles in organic light emitting diodes Toshiki Yamad, Dechun Zou, I , Hyein Jeong, Yoji Akaki, Tetsuo Tsutsui Abstract Recoverable degradation of a polyurethane (PU) derivative with large dipoles on the side chain was investigated. Spontaneous recovery and reverse bias-assisted recovery were Observed. The observed spontaneous recovery and reverse bias-assisted recovery are explained by the formation of in internal electronic field due to the re-orientation of dipoles. The re-orientation of dipoles was evaluated by second harmonic generation measurement. The relatively large estimated value of xzyy, approximately 7 10-7 esu (2.93 10-10 m/V) at 10 V, indicates a high degree of orientation of dipoles, which generates a relatively large internal electronic field.