High-efficiency red electroluminescence from a narrow recombination zone confined by an organic double heterostructure
Red light-emitting diodes (LEDs) with both a conventional bilayer structure and a double heterostructure (DH) have been investigated. In these LEDs, N,N{prime}-bis-(1-naphthl)-diphenyl-1, 1{prime}-biphenyl-4,4{prime}-diamine (NPB), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and tris(8-quinolinolato) aluminum (Alq{sub 3}) were used as hole-transporting, hole-blocking, and electron-transporting layers, respectively. The bilayer and DH LEDs had a configuration of ITO/NPB/Alq{sub 3}:red dopant/Alq{sub 3}/MgAg and ITO/NPB/Alq{sub 3}:red dopant/BCP/Alq{sub 3}/MgAg, respectively. Three kinds of red fluorescent dyes -- nile red, DCJTB, and DCM -- were used as dopants. Compared with the bilayer structures, the luminance efficiencies of the DH LEDs were found to increase as much as 100%. We attribute the efficiency enhancement to the formation of a narrow recombination zone, in which both charge carriers and excitons were confined. High charge concentrations in the emissive layer resulted in efficient collision capture in the electron--hole recombination process. Exciton confinement led to improved energy transfer. The two factors were simultaneously operating and consequently benefitted from efficiency enhancement. {copyright} 2001 American Institute of Physics.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40230790
- Journal Information:
- Applied Physics Letters, Vol. 79, Issue 7; Other Information: DOI: 10.1063/1.1390479; Othernumber: APPLAB000079000007001048000001; 004132APL; PBD: 13 Aug 2001; ISSN 0003-6951
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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