Simple white organic light emitting diodes with improved color stability and efficiency using phosphorescent and fluorescent emitters

White organic light emitting diodes (WOLEDs) with both phosphorescent and fluorescent emitting layers (EML) usually adopt an interlayer between them to achieve high efficiency by preventing mutual quenching, but insertion of the interlayer causes a higher operating voltage as well as additional fabrication steps. Here, we demonstrate that simple-structure WOLEDs without an interlayer could be achieved using the combination of phosphor-sensitized-fluorescent red and phosphorescent blue EMLs. In addition, the main cause of the color shift with increasing current density was identified, and the color shift of the WOLED was successfully suppressed by properly balancing emission from the red and blue EMLs. Consequently, a maximum external quantum efficiency of 6.2% (a current efficiency of 14.3 cd/A) and very stable color coordinates of (0.32±0.01,0.42±0.002) were achieved. However, the elimination of an interlayer for the combination with a fluorescent blue EML causes about 50% decrease in the efficiency and ...

[1]  Gregor Schwartz,et al.  Highly efficient white organic light emitting diodes comprising an interlayer to separate fluorescent and phosphorescent regions , 2006 .

[2]  Stephen R. Forrest,et al.  Management of singlet and triplet excitons for efficient white organic light-emitting devices , 2006, Nature.

[3]  S. R. Forrest,et al.  High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer , 2000, Nature.

[4]  Y. Hamada,et al.  Red organic light-emitting diodes using an emitting assist dopant , 1999 .

[5]  Stephen R. Forrest,et al.  White Organic Light‐Emitting Devices for Solid‐State Lighting , 2004 .

[6]  Chia-Fang Wu,et al.  High-efficiency and long-lifetime fluorescent blue organic-emitting device , 2006, SPIE Optics + Photonics.

[7]  Feng Li,et al.  White organic light-emitting devices using a phosphorescent sensitizer , 2003 .

[8]  Yong Qiu,et al.  Blue phosphorescent dye as sensitizer and emitter for white organic light-emitting diodes , 2004 .

[9]  Joseph Shinar,et al.  Förster energy transfer in combinatorial arrays of selective doped organic light-emitting devices , 2004 .

[10]  Stephen R. Forrest,et al.  Blue organic electrophosphorescence using exothermic host–guest energy transfer , 2003 .

[11]  S. Forrest,et al.  High-efficiency top-emissive white-light-emitting organic electrophosphorescent devices , 2005 .

[12]  Tukaram K. Hatwar,et al.  High-efficiency white OLEDs based on small molecules , 2004, SPIE Optics + Photonics.

[13]  Stephen R. Forrest,et al.  High-efficiency yellow double-doped organic light-emitting devices based on phosphor-sensitized fluorescence , 2001 .

[14]  H. Naito,et al.  Charge carrier transport in an emissive layer of green electrophosphorescent devices , 2004 .

[15]  Chihaya Adachi,et al.  100% phosphorescence quantum efficiency of Ir(III) complexes in organic semiconductor films , 2005 .

[16]  G. Cheng,et al.  White organic light-emitting devices based on 4,4′-bis(2,2′-diphenyl vinyl)-1,1′-biphenyl and phosphorescence sensitized 5,6,11,12-tetraphenylnaphthacene , 2005 .

[17]  Stephen R. Forrest,et al.  White organic light-emitting device based on a compound fluorescent- phosphor-sensitized-fluorescent emission layer , 2006 .