High efficiency phosphorescent OLEDs based on the heterostructured light emission and charge injection layers

The light emitting efficiency and the stability of the phosphorescent devices, whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping influenced by the heterostructured emissive layers and charge injection layer, are studied in terms of the charge injection behavior, carrier transporting mobility, and balancing of devices. The enhancement of the light emitting properties (higher efficiency and lower driving voltage) by use of heterostructures at emitting layer, either multilayers or mixing of hole- and electron-transporting materials (such as 4,4",4"-tris(N-carbazolyl)-triphenylamine); TCTA and bis(10-hydroxybenzo[h]quinolinate) beryllium; Bebq2) was characterized. By a design of emitting layer structure for recombination, 30~50lm/W efficiency of devices with Ir(ppy)3 and conventional transporting layer was possible.

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

[2]  S. Forrest,et al.  VERY HIGH-EFFICIENCY GREEN ORGANIC LIGHT-EMITTING DEVICES BASED ON ELECTROPHOSPHORESCENCE , 1999 .

[3]  Stephen R. Forrest,et al.  Efficient electrophosphorescence using a doped ambipolar conductive molecular organic thin film , 2001 .

[4]  Franco Cacialli,et al.  Molecular-scale interface engineering for polymer light-emitting diodes , 2000, Nature.

[5]  Wolfgang Brütting,et al.  Device physics of organic light-emitting diodes based on molecular materials , 2001 .

[6]  H. Chung,et al.  Carrier trapping and efficient recombination of electrophosphorescent device with stepwise doping profile , 2005 .

[7]  Tae-Woo Lee,et al.  Self‐Organized Gradient Hole Injection to Improve the Performance of Polymer Electroluminescent Devices , 2007 .

[8]  S. Forrest,et al.  Highly efficient phosphorescent emission from organic electroluminescent devices , 1998, Nature.

[9]  B. Chin,et al.  Confinement of Charge Carriers and Excitons in Electrophosphorescent Devices: Mechanism of Light Emission and Degradation , 2007 .

[10]  M. Schaer,et al.  Doping‐Induced Charge Trapping in Organic Light‐Emitting Devices , 2005 .

[11]  Richard H. Friend,et al.  Ultrathin Self‐Assembled Layers at the ITO Interface to Control Charge Injection and Electroluminescence Efficiency in Polymer Light‐Emitting Diodes , 1998 .

[12]  Stephen R. Forrest,et al.  Improved energy transfer in electrophosphorescent devices , 1999 .

[13]  Chih-I Wu,et al.  Mixed host organic light-emitting devices with low driving voltage and long lifetime , 2005 .