Cathodes incorporating thin fluoride layers for efficient injection in blue polymer light-emitting diodes

Thomas M. Brown; Ian S. Millard; David Lacey; Jeremy H. Burroughes; Richard H. Friend; Franco Cacialli

doi:10.1117/12.457463

27 February 2002 Cathodes incorporating thin fluoride layers for efficient injection in blue polymer light-emitting diodes

Thomas M. Brown, Ian S. Millard, David Lacey, Jeremy H. Burroughes, Richard H. Friend, Franco Cacialli

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Proceedings Volume 4464, Organic Light-Emitting Materials and Devices V; (2002) https://doi.org/10.1117/12.457463
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

Abstract

Efficient blue Polymer Light-Emitting Diodes (PLEDs) were fabricated by evaporating thin LiF layers between Al or Ca cathodes. Electroabsorption measurements of the built-in potential across the diodes show that devices fabricated with LiF/Ca/Al cathodes exhibit the smallest average barrier height and operating voltage (compared to both Ca and LiF/Al currently amongst the most efficient electron injectors). The turn-on bias is essentially equivalent to the built-in potential (~2.7 V), indicating an effective minimisation of the barrier to electron injection. Results are also compared with devices incorporating CsF layers and are correlated with the electroluminescent characteristics of the LEDs. A very strong dependence (~ exponential) between the built-in potential and the current and luminance at a fixed electric field (0.5MV/cm) is observed and is explained with the reduction of the cathodic barrier height brought about by the different cathode multilayers.

Citation Download Citation

Thomas M. Brown, Ian S. Millard, David Lacey, Jeremy H. Burroughes, Richard H. Friend, and Franco Cacialli "Cathodes incorporating thin fluoride layers for efficient injection in blue polymer light-emitting diodes", Proc. SPIE 4464, Organic Light-Emitting Materials and Devices V, (27 February 2002); https://doi.org/10.1117/12.457463

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