We report, using modified tirne-of-flight (TOF) apparatus, the measurement of the drift mobility of electrons/holes in thin fihns of vapor-deposited tlis (8-hydroxyquinolinolato) aluminurn (Alq3) and spin-cast poly (N-vinylcarbazole) (PVK) based on silicon. Drift mobilities of both carders are strongly electric field and temperature dependent. At room temperature and an electric field of 2 105Vcm, the effective mobilities of electron and hole are 1

A doping technique for fabricating organic multiple-quantum-well electroluminescent (EL) Devices is demonstrated. This device consists of N,N8-Bis(3-methyphenyl)-N,N8-diphenylbenzidine used as a hole transporter, undoped tris(8-quinolinolato) aluminum (Alq) as a barrier potential or electron transporter, and Alq doped with 5,6,11,12-tetraphenylnaphthacene as a potential well and an emitter. Our experimental results suggest that the double-quantum-well EL devices show the optimum emission characteristics. The efficiency and the luminance of the device achieve 15.7lm/W and 7500 cd/m2, respectively.

Red electrophosphorescence from light-emitting devices based on two rhenium(I) diimine complexes, (4,48-dimethyl formate-2,28-bipyridine)Re(CO)3Cl (dmfbpy-Re) and (4,48-dibutyl formate-2,28-bipyridine)Re(CO)3Cl (dbufbpy-Re), is reported. N, N8-di-1-naphthyl-N, N8-diphenylbenzidine is used as the hole-transporting layer. 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, bathocuproine is used to confine excitons within the luminescence zone. dmfbpy-Re and dbufbpy-Re are doped into the host materials (4,48-N-N8-dicarbazole)biphenyl with mass ratios of 2%-20% as the light-emitting layer. Red emission from both complexes is achieved and the main peaks of both photoluminescence and electroluminescence are at about 610nm. The turn-on voltage, maximum efficiency, and brightness for red emission achieved from the devices based on dmfbpy-Re and dbufbpy-Re are; 5V, 1.3cd/A, and 582 cd/m2 and; 4V, 1.1 cd/A, and 739 cd/m2, respectively.

We demonstrate efficient organic white light-emitting devices (LEDs), using N,N8-diphenyl-N,N8-bis(1-naphthyl)-(1,18-biphenyl)-4,48-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex [(dppy)BF)] as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) as the electron-transporting and chromaticity-tuning layer. The white light comes from exciplex emission at the solid-state interface between (dppy)BF and NPB in addition to the exciton emission from NPB and (dppy)BF, respectively. The chromaticity of white emission can be tuned by adjusting the thickness of the Alq layer. The white LEDs with an Alq thickness of 15nm exhibit a maximum luminescence of 2000cd/m2 and efficiency of 0.58lm/W, and the Commission Internationale De l'Eclairage coordinates of resulting emission vary from (0.29,0.33) to (0.31,0.35) with increasing forward bias from 10 to 25V. The region is very close to the equienergy white point (0.33,0.33).

ZnS:Cu nanocrystals were synthesized in polymeric networks. X-ray photoemission spectroscopy and atomic absorption data show that the Zn and Cu ion mass contents were about 8.2% and 0.12%, respectively. The particle size of ZnS:Cu nanocrystals was about 3.0nm, measured by UV-vis spectrum. Due to the quantum size effects, the band gap energy of ZnS nanocrystals was about 4.2eV. Compared with the photoluminescence of ZnS which peaks at 390nm, the photoemission of ZnS:Cu/polymer thin films was peaking at 415nm because of Cu acting as luminescent centers. The ZnS:Cu/polymer was also used to fabricate light-emitting diode (LED), as the emitting layer of LED, the blue light of electroluminescence was observed at room temperature, and its turn-on voltage was less than 4V.

The hexagonal ZnS nanocrystals were synthesized in polymer matrix. The ZnS polymer composite doped with tetraphenylbenzidine (TPB) as light-emitting layer was used to fabricate a single layer structure light-emitting diode which has a low turn on voltage such as 2.5V. The electroluminescence spectrum was obtained at room temperature. Owing to the effect that TPB interacted with ZnS nanocrystal to form the luminescent center, the emission was peaking at 520nm which shifts to the lower energy compared with that of ZnS, and the half-width of the emission was about 20nm.

White light emission is very important for applying electroluminescent devices to full display, backlight and illumination light source. In this letter, we have reported the white light devices with two sorts of structures. One is organic multi-quantum-well structure. The white light emission spectrum covers a wide range of the visible region, and the Commission Internationale de l'E clairage (C.I.E) co-ordinates of the emitted light are (0.32, 0.38) at 9V. The maximum brightness and luminous ef

We have realized a small-molecule organic light-emitting diode where the intrinsic emitter layer is sandwiched by n- and p-doped transport layers with appropriate blocking layers. The diodes based on this pin concept have exponential forward characteristics up to comparatively high current densities. The diodes reach high brightness at very low operating voltage: for instance, 1000cd/m2 at a voltage of 2.9V. Despite the highly doped transport layers, the devices reach very high efficiency for the given emitter system up to high brightness.

A technique for inducing white-light emission from organic multiheterostructures is proposed. The configuration of organic multiheterostructure white-light emitting diodes is ITO/TPD(5nm)/BePP2(5nm)/TPD(4nm)/BePP2 :rubrene(5nm)/TPD(4nm)/Alq3(10nm)/Al. Triphenyldiamine derivative (TPD) is used as a hole-transporting layer and the potential barrier layers. Blue fluorescent phenylpyridine beryllium (BePP2), orange fluorescent rubrene, and green fluorescent aluminum complex (Alq3) are used as three primary colors. BePP2 and BePP2 doped with rubrene act as the potential wells sandwiched between TPD barrier layers, in which excitons are confined. Alq3 is used as an electron-transporting green-color emitter. The white-light emission spectrum covers a wide range of the visible region, and the Commission Internationale de l'Eclairage coordinates of the emitted light are (0.32, 0.38) at 9V. The maximum brightness and luminous efficiency of this device are 4000 cd/m2 (at 17V) and 0.4lm/W, respectively.

An organic double-quantum-well structure electroluminescent device fabricated by a doping method is demonstrated. The device consists of N,N8-bis-1-naphthl!-N,N8-diphenyl-1,18-biphenyl-4,48-diamine (NPB) used as a hole transporter, undoped tris 8-quinolinolato! aluminum (Alq) as a barrier potential or electron transporter, and Alq doped with 5,6,11,12-tetraphenylnaphthacene (rubrene) as a potential well and emitter, and has the following structure: indium tin oxide/NPB/Alq:rubrene/Alq/Alq:rubrene/Alq/Mg/Al. The maximum brightness and efficiency reach 48000cd/m2 and 4.59lm/W, respectively. The present double-quantum-well structure device shows higher brightness and higher efficiency than those of the common heterostructure devices.