H. S. Bang

Efficiency Stabilization in Blue Organic Light-Emitting Devices Fabricated Utilizing a Double Emitting Layer with Fluorescence and Phosphorescence Doped Layers

The luminance efficiency of the blue organic light-emitting devices (OLEDs) fabricated utilizing a double emitting layer (DEML) with a 4,4′-Bis(2,2-diphenyl-ethen-1-yl)diphenyl (DPVBi) layer doped with 4,4′-Bis[4-(diphenylamino)styryl]biphenyl (BDAVBi) fluorescence dopant and a 4,4′-Bis(carbazol-9-yl)biphenyl (CBP) layer doped with a bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium III (FIrpic) phosphorescence dopant at 20 mA/cm2 was 6.2 cd/A, indicative of highly efficient OLEDs. Electroluminescence spectra for the OLEDs with a DEML showed that a dominant peak at 469 nm corresponding to the BDAVBi doped DPVBi layer together with a shoulder at 491 nm related to the combination of the BDAVBi doped DPVBi layer and the FIrpic doped CBP layer appeared.

Enhancement Mechanisms of the Color Purity in Blue Organic Light-Emitting Devices Fabricated Utilizing an Emitting Layer Containing Mixed Fluorescence and Phosphorescence Host Materials

The electrical and optical properties of blue organic light-emitting devices (OLEDs) containing a mixed host emitting layer (EML) consisting of a 1,3-bis(carbazole-9-yl)benzene (mCP) layer and a 3-tert-butyl-9,10-di(naphtha-2-yl)anthracene (TBADN) layer were investigated. The driving voltage of the OLEDs with a mixed host EML was smaller than that of the OLEDs with a single EML. The electroluminescence spectra for OLEDs containing a mixed host EML showed a dominant peak related to the mCP or the TBADN layer. The color coordinates of the OLEDs containing a 5% TBADN-doped mCP EML were (0.146, 0.091), indicative of the deep blue color coordinates.

Luminance Efficiency Enhancement in Organic Light-Emitting Devices Utilizing 4,7-Diphenyl-1,10-phenanthroline/aluminum tris(8-hydroxyquinoline) Multiple Heterostructures Acting as an Electron Transport Layer

The electrical and optical properties of organic light-emitting devices (OLEDs) with three periods of 4,7-diphenyl-1,10-phenanthroline (BPhen)/aluminum tris(8-hydroxyquinolate) (Alq3) multiple heterostructures acting as an electron transport layer (ETL) were investigated. While the leakage current of OLEDs with multiple heterostructures was smaller than that of OLEDs without multiple heterostructures, the luminance efficiency was larger than that of OLEDs without multiple heterostructures. The BPhen layers in the multiple heterostructures blocked holes from the emitting layer (EML) to the ETL, and they enhanced the electron injection from the cathode to the EML, resulting in an increase in the luminance efficiency.

Enhancement of the Luminance Efficiency of Blue Organic Light-Emitting Devices Fabricated Utilizing a Mixed Host Emitting Layer

The luminance efficiency of the blue organic light-emitting devices (OLEDs) with a mixed host emitting layer (EML) consisting of a 2-t-butyl-9,10-di-2-naphthylanthracene (TBADN) and 4,4′-Bis[4-(diphenylamino)styryl]biphenyl (BDAVBi)-doped 1,3-bis(carbazol-9-yl)benzene (mCP) layer at 20 mA/cm2 was 5.78 cd/A, indicative of highly efficient OLEDs. Electroluminescence spectra for the OLEDs with a mixed host EML showed that a dominant peak at 467 nm corresponding to the BDAVBi doped mCP layer together with a shoulder at 491 nm related to the combination of the TBADN doped mCP layer and the BDAVBi doped mCP layer appeared.

Enhancement of Efficiency Stabilization and Color Purity in Blue Organic Light-Emitting Devices Fabricated Utilizing a CBP/DPVBi Double Emitting Layer

The luminance efficiency as a function of the applied voltage for the blue organic light-emitting devices (OLEDs) with a 4,4′-Bis(carbazol-9-yl)biphenyl (CBP)/4,4′-Bis(2,2′-diphenyl-ethen-1-yl)biphenyl (DPVBi) double emitting layer (DEML) was more stable than that of the OLEDs with a DPVBi emitting layer (EML), a CBP EML, or a DPVBi/CBP DEML, regardless of the variation of the applied voltage. The electroluminescence spectra showed that the dominant peak in the OLEDs with a CBP/DPVBi DEML was shifted to higher energy in comparison to that with a DPVBi EML, a CBP EML, or DPVBi/CBP DEML, indicative of the enhancement of the blue color purity.

Efficiency Enhancement Mechanism of Organic Light-Emitting Devices with an Alq3 Emitting Layer Containing a DPVBi Wide Bandgap Doping Agent

The efficiency of the organic light-emitting devices (OLEDs) with a tris-(8-hydroxyquinoline) aluminum (Alq3) emitting layer (EML) containing a 4,4-bis(2,2diphenyl vinyl)-1,1-biphenyl (DPVBi) doping agent was significantly enhanced in comparison to that with an Alq3 EML without a DPVBi doping agent. The enhancement of the injection efficiency of the OLEDs with an EML doped with a wide-bandgap doping agent was attributed to a decrease in the trap charge density existing in the EML resulting from the existence of the DPVBi doping agent. The luminescence mechanism of the OLEDs fabricated utilizing an Alq3 EML containing a DPVBi wide-bandgap doping agent is described on the basis of the experimental results.