Improved efficiencies in light emitting diodes made with CdSe(CdS) core/shell type nanocrystals and a semiconducting polymer
- Contributions from the Department of Chemistry, University of California, Berkeley
We report experiments on bilayer light emitting diodes made with organically capped CdSe(CdS) core/shell type semiconductor nanocrystals and an electroluminescent (EL) semiconducting polymer [poly(p-phenylenevinylene) or PPV]. The devices emit from red to green with external quantum efficiencies of up to 0.22{percent} at brightnesses of 600cd/m{sup 2} and current densities of 1A/cm{sup 2}. They have operating voltages as low as 4 V and lifetimes under constant current flow of hundreds of hours. Most of these numbers are significant improvements over similar devices made with CdSe nanocrystals. The devices show either nanocrystal-only EL or a combination of nanocrystal and PPV EL, depending on nanocrystal layer thickness. The nanocrystal EL is dependent on nanocrystal size. Some devices show a voltage dependent spectral output. The spectral output is consistent with a field dependent electron range in the nanocrystal layer limited by carrier trapping. {copyright} {ital 1997 American Institute of Physics.}
- OSTI ID:
- 552972
- Journal Information:
- Journal of Applied Physics, Vol. 82, Issue 11; Other Information: PBD: Dec 1997
- Country of Publication:
- United States
- Language:
- English
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