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Electron injection into organic semiconductor devices from high work function cathodes

Author:
Hoven, Corey V., Yang, Renqiang, Garcia, Andres, Crockett, Victoria, Heeger, Alan J., Bazan, Guillermo C., Nguyen, Thuc-Quyen
Source:
Proceedings of the National Academy of Sciences of the United States of America 2008 v.105 no.35 pp. 12730-12735
ISSN:
0027-8424
Subject:
electric field, electrodes, electrolytes, ions, polymers, screening, semiconductors
Abstract:
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.
Agid:
2360045