Since 1993, InGaN light-emitting diodes (LEDs) have been improved and commercialized, but these devices have not fulfilled their original promise as solid-state replacements for light bulbs as their light-emission efficiencies have been limited. Here we describe a method to enhance this efficiency through the energy transfer between quantum wells (QWs) and surface plasmons (SPs). SPs can increase the density of states and the spontaneous emission rate in the semiconductor, and lead to the enhancement of light emission by SP–QW coupling. Large enhancements of the internal quantum efficiencies (etaint) were measured when silver or aluminium layers were deposited 10 nm above an InGaN light-emitting layer, whereas no such enhancements were obtained from gold-coated samples. Our results indicate that the use of SPs would lead to a new class of very bright LEDs, and highly efficient solid-state light sources.

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Surface-Plasmon-Enhanced Light Emitters Based on InGaN Quantum Wells

A lighting device comprising first and second groups of solid state light emitters, which emit light having peak wavelength in ranges of from 430 nm to 480 nm, and first and second groups of lumiphors which emit light having dominant wavelength in the range of from 555 nm to 585 nm. In some embodiments, if current is supplied to a power line, a combination of (1) light exiting the lighting device which was emitted by the first group of emitters, and (2) light exiting the lighting device which was emitted by the first group of lumiphors would have a correlated color temperature which differs by at least 50 K from a correlated color temperature which would be emitted by a combination of (3) light exiting the lighting device which was emitted by the second group of emitters, and (4) light exiting the lighting device which was emitted by the second group of lumiphors.

Lighting device and lighting method

A nitride semiconductor light-emitting device has an active layer of a single-quantum well structure or multi-quantum well made of a nitride semiconductor containing indium and gallium. A first p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided in contact with one surface of the active layer. A second p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided on the first p-type clad layer. The second p-type clad layer has a larger band gap than that of the first p-type clad layer. An n-type semiconductor layer is provided in contact with the other surface of the active layer.

Nitride semiconductor light emitting device

This letter reports a β-SiAlON:Eu2+ green phosphor with the composition of Eu0.00296Si0.41395Al0.01334O0.0044N0.56528. The phosphor powder exhibits a rod-like morphology with the length of ∼4μm and the diameter of ∼0.5μm. It can be excited efficiently over a broad spectral range between 280 and 480 nm, and has an emission peak at 535 nm with a full width at half maximum of 55 nm. It has a superior color chromaticity of x=0.32 and y=0.64. The internal and external quantum efficiencies of this phosphor is 70% and 61% at λex=303nm, respectively. This newly developed green phosphor has potential applications in phosphor-converted white LEDs.

Characterization and properties of green-emitting β-SiAlON:Eu2+ powder phosphors for white light-emitting diodes

We fabricated three types of high luminous efficacy white light emitting diodes (LEDs). The first was a white LED with a high luminous efficacy (?L) of 249?lm?W?1 and a high luminous flux (v) of 14.4?lm at a forward-bias current of 20?mA. This ?L was approximately triple that of a tri-phosphor fluorescent lamp (90?lm?W?1). The blue LED used as the excitation source in this white LED had a high output power (e) of 47.1?mW and a high external quantum efficiency (?ex) of 84.3%. The second was a high-power white LED, fabricated from the above high-power blue LED, and had a high e of 756?mW at 350?mA. v and ?L of the high-power white LED were 203?lm and 183?lm?W?1 at 350?mA, respectively. The third was a high-power white LED fabricated from four high-power blue LED dies. v and ?L of the high-power white LED were 1913?lm and 135?lm?W?1 at 1?A, respectively. The white LED had a higher flux than a 20?W-class fluorescent lamp and 1.5 times the luminous efficacy of a tri-phosphor fluorescent lamp (90?lm?W?1).

https://iopscience.iop.org/article/10.1088/0022-3727/43/35/354002/pdf

White light emitting diodes with super-high luminous efficacy

A light emitting apparatus comprising a light emitting device ( 101 ) disposed on a supporting body ( 105 ), and coating layers (( 108, 109 ) that bind a fluorescent substance that absorbs light emitted by the light emitting device ( 101 ) and emits light of a different wavelength and secures the fluorescent substance onto the surface of the light emitting device ( 101 ). The coating layers ( 108, 109 ) are made of an inorganic material including an oxide and a hydroxide, each containing at least one element selected from the group consisting of Si, Al, Ga, Ti, Ge, P, B, Zr, Y, Sn, Pb and alkali earth metals. Also an adhesive layer ( 110 ) is made of the same inorganic material as that of the coating layers ( 108, 109 ).

Light emitting apparatus and method of manufacturing the same

We fabricated a phosphor-conversion white light emitting diode (LED) using an InGaN chip that emits 400 nm near-ultraviolet (n-UV) light and phosphors that emit in the blue and yellow region. When the white LED was operated at a forward-bias current of 20 mA at room temperature (RT), the color temperature (Tcp), average color rendering (Ra), operating voltage (Vf) and luminous efficacy (ηL) were estimated to be 5800 K, 85.3, 3.2 V, and 26.1 lm/W, respectively. With increasing forward-bias current, the luminous flux increased almost linearly and was estimated to be 5.0 lm at 60 mA. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates obtained from the measured spectra remained almost constant during the forward-bias current increase from 0.5 mA to 60 mA.

https://iopscience.iop.org/article/10.1143/JJAP.41.L371/pdf

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip

A light emitting device, including a light emitting element, and a resin layer that has been screen printed to coat said light emitting element is provided. The resin layer is formed from a curable silicone resin composition, which includes (i) an organopolysiloxane with a polystyrene equivalent weight average molecular weight of at least 5 × 103, (ii) a condensation catalyst, (iii) a solvent, and (iv) a finely powdered inorganic filler. The uniformity of the film thickness is excellent, thus resulting in little color irregularities during light emission from the light emitting element.

Light emitting device with silicone resin layer formed by screen printing

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip : Semiconductors

We fabricated a high-color-rendering, red-enhanced white-light-emitting diode (LED) using a new red phosphor and a short-wavelength YAG phosphor. When the new white-LED was operated at a forward-bias current of 20 mA at room temperature (RT), color temperature (Tcp), the general color rendering index (Ra) and luminous efficiency were 4670 K, 87.7 and 25.5 lm/W, respectively. Most of the color-rendering indexes (CRIs) of the new white-LED were larger than those of current white-LEDs, in which only YAG is used. In particular, the CRI-No.9 value, which shows the color reproduction in the red region, is improved from -2.5 to 62.6.

https://iopscience.iop.org/article/10.1143/JJAP.42.L20/pdf

Kunihiro Izuno

Papers

Light emitting apparatus and method of manufacturing the same

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip

Light emitting device with silicone resin layer formed by screen printing

Phosphor-Conversion White Light Emitting Diode Using InGaN Near-Ultraviolet Chip : Semiconductors

Red-enhanced white-light-emitting diode using a new red phosphor