Miao-Tsai Chu

Suppression of efficiency roll off in blue phosphorescent organic light-emitting devices using double emission layers with additional carrier-transporting material

By employing double emission layers (DELs) into blue phosphorescent organic light-emitting device (PHOLED), the device shows improved current efficiency by a factor of 1.8 as compared with that of device using single emission layer. Furthermore, by doping additional carrier-transporting material into DELs, the device shows only a slight efficiency roll off of 24% from low (1 mA/cm2 and 400 cd/m2) to high current density (40 mA/cm2 and 10 000 cd/m2). The dramatic improvement in device performances can be attributed to the formation of a broader carrier recombination zone and the elimination of carrier accumulation at the interface. A blue PHOLED with a current efficiency of 29.5 cd/A, a power efficiency of 21 lm/W, and a low driving voltage of 4.4 V with a Commission Internationale deL’Eclairage (CIEx,y) of (0.16, 0.35) at a practical brightness of 1000 cd/m2 can be achieved.

Low-voltage, high-efficiency blue phosphorescent organic light-emitting devices

Low-voltage, high-efficiency blue phosphorescent organic light-emitting devices based on a composite emitter, including a wide-band-gap host, a carrier-transporting material, and an organometallic iridium dopant, have been demonstrated. The devices exhibit an external quantum efficiency of 12%, a power efficiency of 17lm∕W and a low voltage of 4.8V at a practical brightness of 1000cd∕m2 with a CIEx,y of (0.16, 0.35), which was twofold higher than that of using the typical emitter composed of host and dopant only. The dramatic enhancement in performance can be attributed to the transport of carriers into the wide-band-gap host, which can be promoted through doping a carrier-transporting material in emitter for increasing carrier recombination.

P-221L: Late-News Poster: New Blue Phosphorescent Host for High-efficiency White OLED

A new blue phosphorescent host with an electron transporting dibenzothiophene molecular skeleton connected to hole transporting carbazolyl moiety has been developed. Using this material, an all-phosphorescent white OLED with a high power efficiency of 60 lm/W, a low driving voltage of 3.6V and a color-rendering index of 75 at practical brightness of 1000 cd/m2 can be achieved.

P‐154: High Efficiency White‐Phosphorescent OLED with Host‐Free Yellow Emitter

A white PHOLED with high power efficiency of 55 lm/W has been demonstrated by using a host-free yellow phosphorescent emitter sandwiched by double blue phosphorescent emitters. The white PHOLED with host-free yellow phosphorescent emitter achieved a comparable device performance to that of using complicated host-guest doped system. Based on this device concept as well as the molecular engineering of blue host material, highly efficient white PHOLED can be achieved.

P-151: Low-Voltage, High-Efficiency Blue Phosphorescent OLED Using Double Emission Layers

Employing double emission layers (DELs) into blue phosphorescent organic light-emitting devices (PHOLED), the device shows improved current efficiency by a factor of 1.8 compared to that of device using single emission layer (SEL). Furthermore, by doping additional carrier-transporting material into DELs, the device shows a slight efficiency roll-off of 24% from low (1 mA/cm2 and 400 cd/m2) to high current density (40 mA/cm2 and 10000 cd/m2). The dramatic improvement in device performances can be attributed to the formation of a broader carrier recombination zone and the elimination of carrier accumulation at interface. A blue PHOLED with a current efficiency of 29.5 cd/A, a power efficiency of 21 lm/W and a low driving voltage of 4.4 V with a CIEx,y of (0.16, 0.35) at a practical brightness of 1000 cd/m2 can be achieved.

P-215: Improved Carrier Transport into Wide-Bandgap Host for Low-Voltage High-Efficiency Blue PHOLEDs

Low-voltage, high-efficiency blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a new composition of emitter, including a wide bandgap host, a carrier-transporting material and an organometallic iridium dopant, have been demonstrated. The device exhibits an external quantum efficiency (EQE) of 12%, a power efficiency of 17 lm/W and a low voltage of 4.8 V at a practical brightness of 1000 cd/m2 with a CIEx,y of (0.16, 0.35), which was twofold higher than that of used typical emitter composed host and dopant only. The dramatic enhancement can attributed to the transport of carrier into the wide bandgap host which can be facilitated through doping a carrier-transporting material in emitter for increasing carrier recombination.

P-219: Color Stability of White Light-Emitting Organic Electroluminescent Device Base on Three Phosphorescent Emission Peaks

Color stability of white organic light emitting diodes (WOLEDs) was developed by three emission peaks. The blue phosphorescent sensitizer was Bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium (Firpic), the orange phosphorescent sensitizer was the thieno-pyridine framework organo-iridium complexes (PO-01), and the red phosphorescent sensitizer was the phenyl-qoinazoline framework organo-iridium complexes (PR-01). An orange/red phosphorescent emitting layer was sandwiched between blue phosphorescent emitting layers. The devices exhibited no change of EL spectra according to the driving voltage. The efficiency of WOLED of 11.6lm/W (17.4Cd/A) at 1000 Cd/m2, a CIE coordinates of (0.43, 0.44), and a CRI of 81. It is good suitability to use in OLED lighting.

A three-spectrum white OLED using green and new red phosphorescent sensitizers

We develop a three-spectrum white organic light-emitting diodes (WOLED) with blue phosphor-sensitized electrofluorescent, green and new red electrophosphorescent emissions. The green phosphorescent sensitizers are bis[5-(trifluoromethyl)-2-(4-fluorophenyl)pyridine]iridium(III)acetylacetonate (Ir-2h) or Bis(2-phenylpyridine) iridium(III)3-Methyl-2,4-pentanedione (Ir(ppy)2mac), and the new red phosphorescent sensitizer is a phenyl-qoinazoline framework organo-iridium complex. The RGB peaks of WOLED with Ir-2h are at a wavelength of 440nm, 516nm, and 633nm, respectively. However, The RGB peaks of WOLED are at a wavelength of 440nm, 550nm, and 625nm, respectively, when the green phosphorescent sensitizer is replaced by Ir(ppy)2mac. Besides, the peak at a wavelength of 550nm is broader than the former. Therefore, The former WOLED of RGB spectra are the most distinct than the later one. The former WOLED has efficiency of 3.3 lm/W (7.15Cd/A) at 1000 Cd/m2, and CIE coordinates of (0.32, 0.35). It is good suitability to use in OLED displays based on RGB color filters and full-color LCD backlights.

P‐145: A Three‐Spectrum White Organic Light Emitting Diode Base on a New Red Organometallic Iridium Complexes

We develop a three-spectrum white OLED (WOLED) made by a new red phosphorescent dopant material. The red dopant material is phenyl-qoinazoline framework organo-iridium complexes. The RGB peaks of WOLED are at a wavelength of 450nm, 512nm, and 633nm, respectively. However, The RGB peaks of WOLED are at a wavelength of 450nm, 512nm, and 572nm, respectively, when the red dopant material is replace by DCJTB. Therefore, The former WOLED of RGB spectra are the most distinct than the later one. The former WOLED has efficiencies of 10.62Cd/A, 6.07lm/W at 100 Cd/m2, and CIE coordinates of (0.28, 0.38). It is good suitability to use in OLED displays based on RGB color filters and full-color LCD backlights.