Namheon Lee

Efficient white organic light emission by single emitting layer

Abstract Stable organic white light-emitting diodes are successfully fabricated by a single organic white emitting layer, which is Bis (2-methyl-8-quinolinato) (triphenylsiloxy) aluminum (III) (SAlq) doped red fluorescent dye of 4-(dicyanomethylene)-2- tert -butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4 H -pyran (DCJTB). The incomplete energy transfer from blue-emitting SAlq to red-emitting DCJTB enables to obtain a stable white balanced light-emission by the DCJTB doping concentration of 0.5%. A device with the structure of ITO/TPD (50 nm)/SAlq:DCJTB (30 nm, 0.5%)/Alq 3 (20 nm)/LiF (0.5 nm)/Al (110 nm) shows maximum luminance of 20xa0400 cd/m 2 at 810 mA/cm 2 , external quantum efficiency of 2% at 200 cd/m 2 (∼3 mA/cm 2 ), power efficiency of 2.3 lm/W at 67 cd/m 2 (∼1 mA/cm 2 ), and a Commission Internationale de lEclairage chromaticity coordinates of (0.34, 0.39) at 1.8 mA/cm 2 to (0.31, 0.38) at 36 mA/cm 2 .

White-light-emitting devices based on organic multilayer structure ☆

Abstract We report an efficient white-light-emitting devices using vacuum-deposited film of a hole-transporting layer of 4,4 ′ bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (α-NPD), a bluish-green emitting layer of bis[2-(2-hydroxyphenyl)benzothiazolate] zinc, a Zn(BTZ) 2 , Zn(BTZ) 2 doped with a red fluorescent dye of 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i, j]quinolizin-8-yl)vinyl]-4H-pyran (DCM2), and an electron-transporting layer of tris(8-hydroxyquinoline) aluminum (Alq 3 ). The incomplete energy transfer from Zn(BTZ) 2 to DCM2 results in the emission of two complementary colors (blue and orange). Controlling the thickness of a Zn(BTZ) 2 layer which acts as a bluish-green emitter and a hole blocking layer and the concentration of DCM2 enables tailoring of the spectral output of the device to have a balanced white emission. A device with the structure of ITO/α-NPD (50 nm)/Zn(BTZ) 2 (4 nm)/Zn(BTZ) 2 :DCM2 (10 nm, 0.8%)/Alq 3 (30 nm)/LiF(0.5 nm)/Al shows an external quantum efficiency (QE) of about 0.5%, a luminous efficiency of 0.27 lm/W, and the CIE chromaticity coordinates of (0.36, 0.33) at luminance 100 cd/m 2 .

Characterization of white electroluminescent devices fabricated using conjugated polymer blends

We report the characterization of white light emitting devices fabricated using conjugated polymer blends. Blue emissive poly[9,9-bis(4-n-octyloxyphenyl)fluorene-2, 7-diyl-co-10-(2-ethylhexyl)phenothiazine-3,7-diyl] [poly(BOPF-co-PTZ)] and red emissive poly(2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene) (MEH-PPV) were used in the blends. The inefficient energy transfer between these blue and red light emitting polymers (previously deduced from the photoluminscence (PL) spectra of the blend films) enables the production of white light emission through control of the blend ratio. The PL and electroluminescence (EL) emission spectra of the blend systems were found to vary with the blend ratio. The EL devices were fabricated in the indium tin oxide [poly(3,4-ethylenedioxy-thiophene)-poly(styrenesulfonate)] (ITO/PEDOT-PSS)blend/LiF/Al configuration, and white light emission was obtained for one of the tested blend ratios.

Efficient white organic light‐emitting device by utilizing a blue‐emitter doped with a Red Fluorescent Dopant

Abstract We synthesized bis (2‐methyl‐8‐quinolinolato)(triphenylsiloxy) aluminum (III) (SAlq), a blue‐emitting material having a high luminous efficiency, through a homogeneous‐phase reaction. The photoluminescence (PL) and electroluminescence (EL) spectra of SAlq show two peaks at 454 nm and 477 nm. Efficient white light‐emitting devices are fabricated by doping SAlq with a red fluorescent dye of 4‐dicyanomethylene‐2‐methyl‐6‐{2‐(2,3,6,7‐tetrahydro‐lH,5H‐benzo[i,j]quinolizin‐8‐yl)vinyl}‐4H‐pyran (DCM2). The incomplete energy transfer from blue‐emitting SAlq to red‐emitting DCM2 results in light‐emission of both blue and orange colors. Devices with the structure of ITO/TPD (50 nm)/SAlq:DCM2 (30 nm, 0.5 %)/Alq3 (20 nm)/LiF (0.5 nm)/Al show EL peaks at 456 nm and 482 nm originating from SAlq and at 570 nm from DCM2, resulting in the Commission Internationale dEclairage (CIE) chromaticity coordinates of (0.32, 0.37). The device exhibits an external quantum efficiency of about 2.3 % and a luminous efficiency of about 2.4 lm/W at 100 cd/m2 . A maximum luminance of about 23,800 cd/m2 is obtained at the bias voltage of 15 V.

P-80: Efficient Organic White Light-Emitting Devices with Multicolor Emitting Layers

We report efficient white organic light-emitting devices consisting of a blue-emitting layer of 1,4-bis(2,2-diphenyl vinyl)benzene (DPVBi) and a red-emitting layer of both 4-dicyanomethylene-2- methyl-6-[2-(2,3,6,7-tetrahydro-1H, 5H-benzo[i, j]quinolizin-8-yl)vinyl]-4H-pyran) (DCM2) and rubrene doped into tris(8- hydroxyquinoline) aluminum (Alq3). The devices show a white light-emission with the Commission Internationale dEclairage (CIE) chromaticity coordinates of (0.34, 0.30). The external quantum efficiency is 2.5 % and luminous efficiency is 1.1 lm/W at a luminance of 100 cd/m2.