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Electron injection into organic semiconductor devices from high work function cathodes
- Hoven, Corey V., Yang, Renqiang, Garcia, Andres, Crockett, Victoria, Heeger, Alan J., Bazan, Guillermo C., Nguyen, Thuc-Quyen
- Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.35 pp. 12730-12735
- electric field, electrodes, electrolytes, ions, polymers, screening, semiconductors
- We show that polymer light-emitting diodes with high work-function cathodes and conjugated polyelectrolyte injection/transport layers exhibit excellent efficiencies despite large electron-injection barriers. Correlation of device response times with structure provides evidence that the electron-injection mechanism involves redistribution of the ions within the polyelectrolyte electron-transport layer and hole accumulation at the interface between the emissive and electron-transport layers. Both processes lead to screening of the internal electric field and a lowering of the electron-injection barrier. The hole and electron currents are therefore diffusion currents rather than drift currents. The response time and the device performance are influenced by the type of counterion used.