White organic light-emitting diodes based on tandem structures

• Published in: Applied physics letters 2005-10, Vol.87 (17), p.173510-173510-3
• Main Authors: Guo, Fawen, Ma, Dongge
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.2120898

White organic light-emitting diodes made of two electroluminescent (EL) units connected by a charge generation layer were fabricated. Thus, with a tandem structure of indium tin oxide/ N , N ′ -di(naphthalene-1-yl)- N , N ′ -diphenyl-benzidine (NPB)/9,10-bis-( β -naphthyl)- anthrene (ADN)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(8-hydroxyquinoline) aluminum ( Al q 3 ) ∕ BCP : Li ∕ V 2 O 5 ∕ NPB ∕ Al q 3 : 4 -(dicyanomethylene)-2- t -butyle-6-(1,1,7,7- tetramethyljulolidyl-9-enyl)4H-pyran ( DCJTB ) ∕ Al q 3 ∕ Li F ∕ Al , a stable white light with Commission Internationale De L'Eclairage chromaticity coordinates from (0.35, 0.32) at 18 V to (0.36, 0.36) at 50 V was generated. It was clearly seen that the EL spectra consist of red band at 600 nm due to DCJTB, green band at 505 nm due to Al q 3 , and blue band at 435 nm due to ADN, and the current efficiency and brightness equal basically to the sum of the two EL units. As a result, the tandem devices showed white light emission with a maximum brightness of 10 200 cd ∕ m 2 at a bias of 40 V and a maximum current efficiency of 10.7 cd ∕ A at a current density of 3.5 mA ∕ cm 2 .