Inorganic semiconductor light-emitting diodes (LEDs) are environmentally benign and have already found widespread use as indicator lights, large-area displays, and signage applications. In addition, LEDs are very promising candidates for future energy-saving light sources suitable for office and home lighting applications. Today, the entire visible spectrum can be covered by light-emitting semiconductors: AlGaInP and AlGaInN compound semiconductors are capable of emission in the red to yellow wavelength range and ultraviolet (uv) to green wavelength range, respectively. Currently, two basic approaches exist for white light sources: The combination of one or more phosphorescent materials with a semiconductor LED and the use of multiple LEDs emitting at complementary wavelengths. Both approaches are suitable for high efficiency sources that have the potential to replace incandescent and fluorescent lights. In this article, the properties of inorganic LEDs will be presented, including emission spectra, electrical characteristics, and current-flow patterns. Structures providing high internal quantum efficiency, namely, heterostructures and multiple quantum well structures, will be discussed. Advanced techniques enhancing the external quantum efficiency will be reviewed, including resonant-cavities, die shaping (chip shaping), omnidirectional reflectors, and photonic crystals. Different approaches to white LEDs will be presented and figures-of-merit such as the color rendering index, luminous efficacy, and luminous efficiency will be explained. Finally, the packaging of low power and high power LED dies will be discussed.


Keywords:

light-emitting diodes (LEDs);
solid-state lighting;
compound semiconductors;
device physics;
reflectors;
resonant cavity LEDs;
white LEDs;
packaging

Light Emitting Diodes

The present invention provides a heterocyclic compound and an organic light-emitting device including the heterocyclic compound. The organic light-emitting devices using the heterocyclic compounds have high-efficiency, low driving voltage, high luminance and long lifespan.

Organic light-emitting device

Electroluminescent devices based on organic materials are of considerable interest owing to their attractive characteristics and potential applications to flat panel displays. After a brief overview of the device construction and operating principles, a review is presented on recent progress in organic electroluminescent materials and devices. Small molecular materials are described with emphasis on their material issues pertaining to charge transport, color, and luminance efficiencies. The chemical nature of electrode/organic interfaces and its impact on device performance are then discussed. Particular attention is paid to recent advances in interface engineering that is of paramount importance to modify the chemical and electronic structure of the interface. The topics in this report also include recent development on the enhancement of electron transport capability in organic materials by doping and the increase in luminance efficiency by utilizing electrophosphorescent materials. Of particular interest for the subject of this review are device reliability and its relationship with material characteristics and interface structures. Important issues relating to display fabrication and the status of display development are briefly addressed as well.

https://ir.nctu.edu.tw:443/bitstream/11536/28337/1/000179449700001.pdf

Recent progress of molecular organic electroluminescent materials and devices

An object of the present invention is to decrease the resistance of a power supply line, to suppress a voltage drop in the power supply line, and to prevent defective display. A connection terminal portion includes a plurality of connection terminals. The plurality of connection terminals is provided with a plurality of connection pads which is part of the connection terminal. The plurality of connection pads includes a first connection pad and a second connection pad having a line width different from that of the first connection pad. Pitches between the plurality of connection pads are equal to each other.

Semiconductor device and display device

A multicolor organic light emitting device employs vertically stacked layers of double heterostructure devices which are fabricated from organic compounds. The vertical stacked structure is formed on a glass base having a transparent coating of ITO or similar metal to provide a substrate. Deposited on the substrate is the vertical stacked arrangement of three double heterostructure devices, each fabricated from a suitable organic material. Stacking is implemented such that the double heterostructure with the longest wavelength is on the top of the stack. This constitutes the device emitting red light on the top with the device having the shortest wavelength, namely, the device emitting blue light, on the bottom of the stack. Located between the red and blue device structures is the green device structure. The devices are configured as stacked to provide a staircase profile whereby each device is separated from the other by a thin transparent conductive contact layer to enable light emanating from each of the devices to pass through the semitransparent contacts and through the lower device structures while further enabling each of the devices to receive a selective bias. The devices are substantially transparent when de-energized, making them useful for heads-up display applications.

Transparent contacts for organic devices

A multi-color light-emitting element has at least two optical micro-cavity structures (102-106) having respectively different optical lengths determining their emission wavelengths. Each micro-cavity structure contains a film (105) of organic material as a light-emitting region. These may be a single film (105) of uniform thickness in the element.

Light-emitting elements.

Luminescent spectra of organic thin films sandwiched with two mirrors were measured in an effort to detect optical microcavity effects. Narrowing and enhancement of photoluminescent spectra were observed from the tri‐(8‐hydroxyquinolinol)aluminum monolayer with the mirrors at both sides. Furthermore, the narrowing of spectra was also observed from electroluminescent devices fabricated with two mirrors.

Organic photo- and electroluminescent devices with double mirrors

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device hydrophobizing a porous insulating film. SOLUTION: The method includes steps of: (S101) forming the porous insulating film 2 on a substrate 3; (S102) arranging the substrate 3 on which the porous insulating film 2 is formed in a chamber 1; (S103) introducing siloxane in the chamber 1 in which the substrate 3 is arranged, and raising the temperature of the substrate 3 to a first temperature; and (S104) raising the temperature of the substrate 3 on which introduced siloxane is attached to a second temperature higher than the first temperature. In S103, the pressure in the chamber 1 is set to be equal to or smaller than 1 kPa. The first temperature is equal to or greater than a temperature at which the pressure in the chamber 1 becomes the saturation vapor pressure of siloxane, and equal to or lower than a temperature at which polymerization reaction between the porous insulating film 2 and siloxane is started. COPYRIGHT: (C)2011,JPO&INPIT

Method for manufacturing semiconductor device

Yttrium oxide (Y2O3) thin films were deposited on indium‐tin‐oxide(ITO)‐coated glass substrates by the radio‐frequency‐sputtering method using an Y2O3‐sintered target. The relative dielectric constant er and the dielectric strength EBD of the Y2O3 films were studied. It was found that er and EBD have a maximum value and a minimum value, respectively, at 1.3 Pa when the pressure of the sputtering gas, Ar+10% O2, is varied from 0.67 to 9.3 Pa. The x‐ray diffraction study showed that the Y2O3 films deposited at 1.3 Pa are predominantly oriented along the 〈332〉 direction and their grain size is the smallest. Ion mass analysis showed impurity diffusion from ITO in the films deposited at 1.3 Pa. Furthermore, the dielectric properties of the Y2O3 films deposited at 1.3 Pa are related to the structural properties, such as the 〈332〉 orientation, grain size, and impurity diffusion.

Dielectric properties of rf‐sputtered Y2O3 thin films

A resonance type variable wavelength luminescent device which can control a spectrum of emission light of luminescent elements in response to an input signal such as voltage, heat, pressure, sound wave, magnetic field, electric field, gravity, electromagnetic wave or the like. Sequentially formed as laminated on a glass substrate are a semi-transparent reflective film, first electrically conductive transparent electrode films, a variable optical length layer, second electrically conductive transparent electrode films, a hole injection layer, an active layer made of aluminum chelate or the like and metallic electrodes, so that the first and second electrically conductive transparent electrode films are mutually arranged in a matrix form. A voltage is applied between the second electrically conductive transparent electrode films and the metallic electrodes to cause light emission of the active layer, whereas a voltage is applied between the first and second electrically conductive transparent electrode films to control the optical length of the variable optical length layer and to control a spectrum of emission light of the device. The variable wavelength luminescent device can be applied to planar color displays, optical switches and various sorts of sensors.

Takahiro Nakayama

Papers

Light-emitting elements.

Organic photo- and electroluminescent devices with double mirrors

Method for manufacturing semiconductor device

Dielectric properties of rf‐sputtered Y2O3 thin films

Variable wavelength luminescent device and control method therefor