1. Photonics Center, Nankai University, Tianjin 300071，China 2. Institute of Polymer Optoelectronic Materials & Devices (IPOM), South China University of Technology, Guangzhou 510640，China 3. Dupont Displays, California, USA; Visiting Professor of Nankai University, Tianjin 300071，China
Abstract：The authors report Raman degradation study of polymer light-emitting devices under ambient conditions. In order to investigate the chemical degradation reaction in polymer light-emitting diode (PLEDs) devices, the chemical structure of the poly (2-(4-Ethylhexyl) phenyl-1, 4-phenylene vinylene) (P-PPV) polymer was analyzed by micro-Ramam spectroscopy during the lifetime of the devices. The evidence for the reduction of conjugation length is provided by Raman spectroscopy. This reduction of the conjugation length，which dramatically increases the resistance and cuts off the current density，was the main reason for the failure of lighting. These findings provide an important insight into the intrinsic degradation mechanisms of the polymer LEDs and help in the development of even more stable devices.
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