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′-bis-(1-naphthl)-diphenyl-1, 1′-biphenyl-4,4′-diamine (NPB), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and tris(8-quinolinolato) aluminu...

Full description

Saved in:
Bibliographic Details
Published in:Applied physics letters 2001-08, Vol.79 (7), p.1048-1050
Main Authors: Xie, Z. Y., Hung, L. S., Lee, S. T.
Format: Article
Language:English
Subjects:
ALUMINIUM
CHARGE CARRIERS
CONFIGURATION
CONFINEMENT
EFFICIENCY
ELECTROLUMINESCENCE
ENERGY TRANSFER
EXCITONS
PHYSICS
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
RECOMBINATION
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Red light-emitting diodes (LEDs) with both a conventional bilayer structure and a double heterostructure (DH) have been investigated. In these LEDs, N,N′-bis-(1-naphthl)-diphenyl-1, 1′-biphenyl-4,4′-diamine (NPB), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), and tris(8-quinolinolato) aluminum (Alq3) were used as hole-transporting, hole-blocking, and electron-transporting layers, respectively. The bilayer and DH LEDs had a configuration of ITO/NPB/Alq3:red dopant/Alq3/MgAg and ITO/NPB/Alq3:red dopant/BCP/Alq3/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.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.1390479