Chikayoshi Morishima

Fabrication and characteristics of 8‐hydroxyquinoline aluminum/aromatic diamine organic multiple quantum well and its use for electroluminescent diode

Multiple quantum well structure consisting of alternating layers of organic 8‐hydroxyquinoline aluminum (Alq3) and aromatic diamine (TPD) has been grown by organic molecular beam deposition. The multiple quantum well structure was determined by x‐ray diffraction, optical absorption, and photoluminescence. Photoluminescence peak of Alq3 shifts to higher energy with decreasing layer thickness, suggesting a quantum size effect. An electroluminescent diode has also been fabricated by using Alq3/TPD multiple quantum well structure.

Observation of spectral narrowing and emission energy shift in organic electroluminescent diode utilizing 8‐hydroxyquinoline aluminum/aromatic diamine multilayer structure

Organic electroluminescent (EL) diode with a multilayer structure which consists of alternating layers of organic 8‐hydroxyquinoline aluminum (Alq3) and aromatic diamine has been grown by organic molecular beam deposition. The EL emission from the multilayer structure shows spectral narrowing and the emission energy has been observed to shift to higher energy compared with that in the monolayer structure. Mechanism of spectral narrowing and the emission energy shift in the diode with the multilayer structure have been discussed.

Visible and blue electroluminescent diodes utilizing poly(3-alkylthiophene)s and poly(alkylfluorene)s

Abstract Visible red-orange poly(3-alkylthiophene) and blue poly(alkylfluorene) electroluminescent diodes have been successfully fabricated and the emission characteristics of the diode have been discussed. The electroluminescent diodes consist of thin polymer films sandwiched by ITO and Mg alloy electrodes. The dependence of emission intensity on alkyl-side-chain shows that the longer the alkyl-side-chain length is, the stronger the emission intensity of poly(3-alkylthiophene) diode is. The diode emits red-orange light having a broad band peaked at 640 nm, which correspond to the band gap of the poly(3-alkylthiophene). Novel temperature dependence of electroluminescence intensity has also been discussed. Blue emission centered at 470 nm have also been observed in poly(alkylfluorene) diode. Band diagrams of the electroluminescent diodes have also been discussed.

Time-resolved pulse response of electroluminescence in poly(3-alkylthiophene) diodes

Pulse response of electroluminescence in poly(3-alkylthiophene) diodes has been investigated. The response consists of two independent parts, that is, fast and slow transition parts. The fast response corresponds to carrier transit between electrodes. On the other hand, the anomalous slow response which becomes marked at higher current is explained by the temperature change of the diode junction. Carrier mobility of the poly(3-alkylthiophene) has been estimated from the fast part, which coincides with that evaluated from the characteristics of poly(3-alkylthiophene) field-effect transistors. Temperature dependence of the electroluminescence intensity in poly(3-alkylthiophene) diode has been discussed.

Enhancement of emission efficiency in electroluminescent diode utilizing vapor-deposited poly(alkylfluorene)

An electroluminescent diode utilizing vapor-deposited poly(alkylfluorene) has been demonstrated. Efficiency of electroluminescence has been increased by using vapor deposition of poly(alkylfluorene) as an emitting layer. A three layered structure of poly(alkylfluorene) diode has been fabricated using the vapor deposition technique. The energy band diagram is discussed for the layered structure of the diode.

Photoluminescence Quenching under Reverse Bias in Organic Multilayer Structure Utilizing 8-Hydroxyquinoline Aluminum and Aromatic Diamine

Photoluminescence intensity from an organic multilayer structure utilizing 8-hydroxyquinoline aluminum ( Alq3) and aromatic diamine (TPD) has been modulated by applying reverse bias voltage. Photoluminescence intensity decreases with increasing reverse bias voltage. The decrease of photoluminescence intensity is enhanced in the thinner multilayer structure compared with the thicker multilayer. The mechanism of photoluminescence quenching in the organic multilayer structure has been discussed.

Fabrication and optical characteristics of an organic multi-layer structure utilizing 8-hydroxyquinoline aluminium/aromatic diamine and its application for an electroluminescent diode

A thin film multi-layer structure consisting of alternating layers of organic 8-hydroxyquinoline aluminium (Alq3) and aromatic diamine (TPO) has been grown by organic molecular beam deposition. The structure of the multi-layer has been confirmed by X-ray diffraction. Optical characteristics have been studied using optical absorption and photoluminescence. The photoluminescence peak of Alq3 shifts to a higher energy with decreasing layer thickness, suggesting a quantum size effect. An electroluminescent diode has also been fabricated using the Alq3/TPD multi-layer structure, and the emission characteristics have also been discussed.

Schottky Gated Field Effect Transistors and Visible Electroluminescent Diodes Utilizing Poly(3-alkylthiophene)s

Abstract Fabrication and characteristics of Schottky gated field effect transistors (FETs) and visible electroluminescent (EL) diodes utilizing poly(3-alkylthiophene)s have been presented. The FETs show typical enhancement type metal-semiconductor FET characteristics. Large temperature dependence and gas-sensitivity have been found for poly(3-alkylthiophene) FETs. Visible red-orange poly(3-alkylthiophene) EL diodes have been successfully fabricated utilizing poly(3-alkylthiophene)s with long alkyl-side-chain. The emission intensity increases with increasing alkyl-side-chain length. Current-emission intensity characteristics show super-linear increase of the emission intensity with increasing injection current. Temperature dependence of emission intensity has been discussed. Camer mobility has also been evaluated from the pulse response of the emission.

Novel characteristics of electroluminescent diode with organic superlattice structure utilizing 8-hydroxquinoline aluminume and aromatic diamine

Summary form only given, as follows. Novel optical characteristics of superlattice structure diode which consist of alternate layers of fluorescent molecules 8-hydroxquinoline aluminum (Alq3) and aromatic diamine (TPD) have been presented. Photoluminescence intensity from Alq3 has been enhanced in the superlattice structure and the intensity has been modulated under reverse biased condition as shown in Fig. 1. The dependence on electric field is stronger in the thinner layer of superlattice, which is explained by the interaction among photoexcited excitons, the reverse biased field and the carrier confinement. Exciton dynamics and the quantum size effect has been discussed in the superlattice structure. The electroluminescent (EL) diode consists of superlattice structure shows spectral narrowing and the emission energy shift compared with the conventional heterostructure diode. Carrier and exciton confinements have been discussed in the EL diode with superlattice structure considering the energy band scheme.

Efficient Energy Transfer in Organic Multilayer Structure Utilizing 8-Hydroxyquinoline Aluminum and Aromatic Diamine

Photoluminescence from an organic multilayer structure utilizing 8-hydroxyquinoline aluminum ( Alq3) and aromatic diamine has been discussed in terms of the wavelength of the excitation light and the layer thickness. The photoluminescence intensity from Alq3 layers is enhanced in the thinner multilayer structure compared with the thicker one as a result of efficient energy transfer at the heterointerfaces. The mechanism behind the increase of photoluminescence intensity in the organic multilayer structure is discussed.