Short-term degradation behaviors of light emitting diodes made of polyurethane derivative with large permanent dipoles on the side chain

The effect of permanent dipole on the performance of organic electrolumines cent devices (OELDs) was investigated by using a model polyurethane derivat ive (PU) with large dipoles on its side chain. The used OLEDs emits green c olor with an emission maximum at 540 nm. Decreases in luminance and current density during a constant voltage driving were observed. Evident spontaneo us recovery and reverse bias assisted recovery of the degradation were conf irmed. The observed degradation and recovery phenomena were discussed in te rms of internal electronic field formation due to the re-orientation of dip ole in organic layer. (C) 2000 Elsevier Science S.A. All rights reserved.