China's semiconductor lighting industry in recent years in output,
output value and technical indicators have made breakthrough
development. In 2014, China's semiconductor lighting, lighting output
value of 950 billion yuan, an increase of 43.9%. Among them, LED
lighting products exports 90 billion US dollars, up 50%, LED lighting
penetration rate of 20%. The first half of 2015, LED lighting products
increased by about 23% year on year, 1 to May exports of 4.08 billion US
dollars, a considerable year-on-year.
From the latest developments in global semiconductor lighting, the
level of the global LED device luminous efficiency laboratory has more
than 300lm / w, the industrialization level of 150lm / w or more, LED
light efficiency of the laboratory level of light up to 200lm / w. The
United States to adjust the target SSL device for the industrialization
of light efficiency level of 250lm / w, LED light efficiency of the
industrialization of the whole level of 200lm / w. In short, LED
lighting products, such as penetration, luminous efficiency and the
theoretical value and target value there is a big gap, the technology
also need to have a greater breakthrough.
LED lighting technology presents eight major trends
LED lighting technology involves a wide range of multi-disciplinary
technology and modern information technology, the development of eight
technology development trend.
First, to improve the efficiency of LED lighting the entire lamp: LED
light energy efficiency at this stage consists of six parts: the quantum
efficiency, chip take light efficiency, packaging efficiency, phosphor
excitation efficiency, lamp efficiency and power efficiency. In a
certain boundary conditions, the theoretical value is 58%, better
lighting energy efficiency is only 30% more, there is great room for
advancement, the above six must reach more than 90% for the job, you
need a technical breakthrough.
The second is to improve the LED light source light color quality and
color characterization value: LED light source to improve the light
color quality, to use RGB multi-spectral combination, that is,
multi-chip combination or multi-color phosphor combination to achieve a
reasonable amount of LED spectral distribution SPD , But also to control
the main light color parameters, such as color tolerance, glare,
photoelectric flicker. LED light source color rendering characterization
is a long-term controversial topic, LED light source can achieve more
flexible combination of multi-spectral, using any of the parameters of
the color characterization, are flawed, the ultimate characterization
may be in the form of spectra. Some experts have proposed using color
gamut index (GAT) together with CRI to characterize the reduction of
light on the color.
Third, LED lighting technology innovation: LED light source, lighting
is currently the most important LED lighting industry, technology to
accelerate the lighting shape and control features of innovation,
specifically the shape of the lamp shape creativity, size, flexibility,
light volume on demand adjustment , Light color and flexible changes,
such as the installation location at random.
The fourth is to carry out intelligent lighting research and
development and application: Intelligent lighting technology features
include open, distributed, remote telemetry, compatibility, interactive,
lighting and information technology is the depth of integration. The
technology involves a wide range of key technologies, light-emitting
modules and the interface between the drive power integration, the
current urgent need for a unified basic standards, according to the
actual needs of research and development to promote the application.
Five is to expand LED lighting applications: to promote the application
of non-visual lighting systems, such as health care, ecological
agriculture, LED visible light communication and infrared LED and UV LED
applications, this content is rich, application technology is
developing rapidly. LED display applications focus on the development of
high-definition small-pitch display and high-definition flexible
display technology to achieve high-definition LED TV and HD folding,
wearable display device.
Sixth, narrow spectral LED device research: a single LED narrow
spectrum can be achieved combined LED spectral flexibility, LED display
can achieve greater color gamut space, is a big application areas, to
achieve narrow spectral LED device technology to From the material
epitaxial on a breakthrough.
Seven is the white LED devices will gradually shift to RGB Combination:
RGB combination of white theory with a higher light efficiency, and
convenient dimmer, color, tone color, etc., to focus on improving the
green LED light effect , RGB combination may become the mainstream of
ordinary lighting.
Eight is a natural light lighting will be the ultimate goal: With the
development of LED multi-spectral lighting, people will pay more
attention to energy saving lighting, health lighting and ecological
lighting, using similar sunlight will be the best choice, that is,
natural lighting, the use of LED Technology can be achieved, but to
solve many technical problems.
LED lighting technology has great room for development, but also need
to further improve the energy efficiency of the entire lamp and light
quality. In the application to actively promote the innovation of lamps
at the same time, we must continue to expand applications, such as
intelligent lighting, non-visual lighting and high-definition display;
technology to achieve the ultimate goal, namely natural lighting, to
provide energy saving, healthy and comfortable lighting surroundings.
Development Trend of Nanoscale Luminescent New Material Technology
At this stage three types of nano-luminous new material technology
developments, perhaps the future lighting of the light source.
Quantum Dot Emission Technique
Quantum dot light-emitting technology in recent years has developed rapidly, is the field of light in the new technology line.
Quantum dots: Quantum dots (QD) are made of nanotechnology, QD
particles are generally between 2nm ~ 12nm, quantum dots from the
light-emitting core, semiconductor shell, organic ligands, such as
luminescence CdSe (cadmium selenide ) QD particles, the advantage is:
can emit visible light to infrared, luminous stability, the quantum
efficiency of up to 90%, combined with the LED produce rich colors, very
bright warm white.
3D printing QD-LED: Princeton University for the first time to display
3D print quantum dot LED, the bottom layer is composed of nano-silver
particles, the top two polymers are indium gallium, quantum dots are
nano-cadmium selenide particles, the shell is zinc sulfide package , The
cadmium selenide nanoparticles emit different visible light after the
connection of the upper and lower electrodes, and the QD-LED is printed
on a device having a curved surface such as a contact lens. The
technology will be extended to 3D printing of other active devices, such
as MEMS, transistors, solar cells and so on. Once the industrialization
will be disruptive innovation technology.
Ultraviolet (UV) QD-LED: The University of Notre Dame is developing
Gallium Nitride (QD) QDs whose electron holes pass through the tunnel
(electron-penetrating barrier phenomenon) rather than the traditional
drift-diffusion. Can be made of ultraviolet (UV) LED, made great
progress, a detailed article reported.
Quantum Dot Hybrid LED: Hiroshima University, Japan Research quantum
dot inorganic / organic hybrid light-emitting diode, can be issued
white, blue, power supply voltage 6V, 78% of the effective light from
the silicon quantum dots, 350 times higher output power density. New LED
at room temperature and pressure through the solution processing
process, known as the lighting system on a new revolution.
Quantum-dot electrical excitation blue LED: Taitung University and the
Far East University of cooperation to colloidal quantum dots of cadmium
sulfide, zinc sulfide to produce electrical excitation blue
light-emitting diodes, similar to the organic inorganic material to do,
high reliability, can replace the OLED in the plate On the application.
Quantum dot backlight technology: embedded quantum dot backlight, the
use of quantum dots embedded optical film (QDEF) used in LCD backlight,
quantum dot in the blue LED backlight illumination, the red, green form
RGB white light. Improve LED luminous efficiency, improve LCD color
saturation, the LCD color gamut increased by 30%, but also increase the
backlight brightness, reduce energy consumption, and has been
industrialized. This TV is expected to produce 1.3 million units in
2015, 2018 amounted to 18.7 million units.
The second generation of quantum dot display technology: Zhejiang
University research team to develop the two, the quantum dots into the
solution, with the crystal and the solution of the dual performance, in
principle, so that electronic slowdown "pace" to promote efficient
electrons and holes meet complex , Greatly enhance the efficiency of
quantum dots LED, performance and stability, quantum efficiency of up to
100%, RGB color rich. Applied to the display and lighting to achieve a
breakthrough.
Graphene luminescence technology: discovery of graphene luminescence is
a new breakthrough, in addition to the growth of graphene on the third
generation of semiconductor substrates.
Graphene light bulbs: Columbia University and Seoul University and
other units to study, the graphene filament attached to the metal
electrode, both sides of SiO2, suspended in the silicon substrate. The
current was heated to over 2500 ° C to give a bright light, and the
temperature of the graphene was not transferred to the substrate. The
use of light-emitting filament and silicon substrate rebound
interference, adjustable emission spectrum, known as the world's
thinnest bulb, and can be applied to optical communications. The
technology such as industrialization will be subversive innovation in
the field of lighting.
Graphene LED: Tsinghua University recently released the use of two
kinds of graphene, that is, graphene oxide (GO) and reduced graphene
(rGO) mixed composition LED, with the applied voltage changes can change
the wavelength of light, the two interfaces there is a Series of
discrete energy levels, in the light, sensors, flexible display
applications.
SiC + graphene + GaN film: Silicon is evaporated on SiC wafer and the
remaining graphene film is reliably transferred to a silicon substrate
on which a direct Van der Waals epitaxy is used to grow high quality
single Crystalline GaN film, will greatly reduce the cost of
semiconductor components. IBM recently announced that it has acquired
these technologies by investing $ 3 billion over five years in
developing high-frequency transistors, photodetectors, biosensors and
post-Si age components on graphene substrates, first by significantly
reducing GaN blue cost.
Glass substrate + graphene + sputtering GaN: Transparent graphene
multilayer film on a glass substrate and forming a GaN (AlN + n-GaN)
film by pulse sputtering (PSD) on a glass substrate, + GaN and InGaN
multi-layer structure MQWs + P-GaN). Its advantages: a substantial
increase in the quality of GaN growth can be produced RGB combination of
three primary colors LED, a significant reduction in costs. Can also be
made of GaN high-mobility transistors (HEMT), the technology line if
the industry will be disruptive innovation.
Graphenea Corporation announced the formation of graphene on copper
foils by common chemical vapor deposition (CVD) in cooperation with
Ritsumeikan University, MIT, Seoul National University, and Dongguk
University of Korea. The GaN crystals were directly transferred onto a
silicon substrate and then grown on graphene using radio frequency
plasma assisted molecular beam epitaxy (RF-MBE), with hexagonal symmetry
growing along the C axis and from the Si (100) plane Growth of the GaN
crystal to achieve the highest quality.
The high-quality GaN grown on these three kinds of graphene substrates
does not adopt MOCVD equipment, and has high growth efficiency, low cost
and high quality. In addition to being used for luminescence and laser,
the third-generation wide bandgap semiconductor can be developed, This
will be disruptive innovation.
Nano-luminous technology
Nano-light-emitting structure is diverse, here are some typical nano-light-emitting structure morphology.
Nano-linear LED: Boer Institute of nano-linear LED, the nanowire core
is GaN material, about 2 microns in length, diameter of about 10 to 500
nm, the external material is InGaN. The light in the diode is determined
by the mechanical tension between the two materials, which can be used
to provide higher brightness with less energy, are more energy
efficient, can be used in cell phones, televisions and many forms of
lighting, Future Lighting World.
Ultra-thin non-crystalline dielectric film Light-emitting material: the
United States Texas Agricultural University to develop a light-emitting
chip, the use of silicon wafers in the room temperature sputtering
deposition method made of dielectric film, including nanocrystalline
layer, can enhance the luminous density, in the process Can be
compatible with silicon IC, the process is simple, is a new
nano-luminescent materials.
3D printing "light paper": Rohinni, Texas, US companies use 3D printing
light paper (Light paper), the ink and micro-LED hybrid printed on the
semiconductor layer, and sandwiched between the other two materials,
micro-LED only red blood cell size, when Electronic through the mini-LED
light paper when lit, known as the world's thinnest LED lights.
Thinnest LED: University of Washington researchers have developed the
world's thinnest LED, the equivalent of three atoms thick, this folding
LED, the future for portable, flexible wearable equipment.
Ultra-high-speed LED: Duke University, the United States through the
metal nano-cubes and gold film between the fluorescent molecules,
high-speed LED, 75 silver nano cube, and trapped inside the light,
increasing the intensity of light, And the photon emission is 1000 times
faster than that of conventional LEDs. It can also be used as a single
photon source for quantum cryptosystems and supports secure optical
communication.
LED close to the sun: Italy InSubria University, the use of
nanoparticle panels on the white LED light source scattering, get close
to the sun light, the use of Rayleigh scattering principle, the white
LED array diffusion "blue sky" effect, or yellowish speckle simulation
Sunlight, the existing products, the effect is good, can greatly enhance
the quality of light color.
Ultra-clear flexible display technology: the use of nanotechnology PCM
phase-change material, can be two states of the so-called GST, crystal
state and glass state, this GST current pulses, the crystal glass cycle
can be more than 1 million times / . Three-layer structure: conductive
glass + GST + conductive glass, each layer is only a few nano-thick,
the technology may produce ultra-thin, ultra-high-speed, low power,
high-definition, folding color display.
Other luminescent materials
White laser: the University of Arizona developed a R, G, B laser can be
mixed into white, can also be used for optical communication, 10 to 100
times faster than ordinary LED.
Nakamura repair II using different technical routes, proposed for the third generation of laser lighting lighting.
Phosphor light-emitting materials: Australian National University found
that thin-layer phosphorescence characteristics, can be used for PV and
LED.
Organic Light Emitting Diode (OLED): has entered the field of flat
lighting, it was predicted that the future will account for a quarter of
the field of lighting.
Perovskite LED: Cambridge University, Oxford University and other joint
development of calcium titanium LED, simple process, low cost, claiming
that 5 years after the LED can be industrialized.
In recent years, nanoscale luminescent new materials technology has
made great progress, especially quantum dot luminescence, graphene
luminescence and nanometer luminescence technology, have pioneering and
disruptive innovation technology, may be the future lighting new light
source, to cause us The industry's attention.
The growth of high-quality crystals on graphene substrates, in addition
to luminescence and lasers, will greatly advance the development of
third-generation wide-band-gap semiconductor materials, supporting the
development of post-silicon era high-performance components.
(Responsible for: Nicole)