A member of staff at Philips sweeps her finger over the screen of her smartphone. All the rectangular lighting elements with gas-discharge lamps high in the ceiling of the truck asmbly hall suddenly rotate a quarter turn, and LEDs (light emitting diodes) take their place. It’s like the rotating number plates on a James Bond car.
We are in one of the many demonstration areas for lighting at the Philips Light division in Eindhoven. The hostess from the electro-nics company is demonstrating the advan-tages of LEDs to a group of a dozen PhD students from Delft. According to Philips, the LED is the light source of the 21st century. LEDs are energy-saving, you can dim them, they have a life of twenty thousand hours and they are small, so they can be worked into all manner of materials.
Not much needs to be explained to the young rearchers. They are all involved in LED-related rearch in clo collaboration with Philips. The visit is an interesting outing for them.
The PhD students’ supervisor is Prof. Kouchi Zhang, who has been part-time professor at the Delft Institute of Microsystems and Nano-electronics (Dimes) for two years. Zhang, who also works for Philips, is a Messiah of the new light. “By 2020, three-quarters of all bulbs will be LEDs”, he says.
Will they all be LED bulbs that you have to screw into a socket? Zhang hopes not. “I pre-dict the liberati
on of light. Retrofit is actually very stupid. If you power LEDs with batteries – and we’re getting better and better at that, becau they’re becoming increasingly ener-gy-efficient - then you no longer need any of the infrastructure with wires and sockets.”
Efficient
LEDs are nothing at all like incandescent bulbs, energy-saving bulbs, gas-discharge lamps or fluorescent tubes. They are chips that work like a solar cell in rever.
The miconductor materials in solar cells absorb photons and current begins to flow, but in LEDs, flows of electrons through the miconductor materials result in photons being emitted. And they currently produce 150 lumen per watt, ten times more efficient than an incandescent bulb.
The fact that LEDs are chips means that all sorts of electronics and nsors can be con-nected to them. What about LEDs fitted into window panes, to measure how much sunlight is shining into a room and provide light when it gets dark outside? Or LEDs with temperature and smoke nsors that mark out the safest escape route when there is a fire?All the things could be possible, claims Zhang’s colleague, Dr Henk van Zeijl. “Ever since Edison invented electric light, it has been imprisoned inside glass. Until shortly after the Second World War, electronic func-
For more than a century, light has come from glass shell. But it won’t for much longer, believes Prof. GQ (Kouchi) Zhang. “Light emitting diodes are going to liberate light.”
Tomas van Dijk
tions were realid with glass; glass radio tubes. When transistors made it possible to make electronics without glass, this brought about a revolution. Something similar is now happening with lighting.”
The rearch of the Delft PhD students focu-s on many different aspects relating to elec-tronics and nsors for LEDs. But the housing for the chip – which to a large extent determi-nes the colour of the light – and techniques
for preventing the bulb from overheating are ‘By 2020, three-quarters of all bulbs will be
LEDs’
A chip the size of a grain of sand lies on the desk of Dr Henk van Zeijl at Dimes. That’s all it is. “When I pass current through it, you mustn’t look directly into the LED,” he explains. “The light is so bright that it would blind you.”In the chip’s miconductor
material there are freely
moving electrons and electron holes. When a current is pasd through the material, the electrons m
ove through the material until they come to a hole that they can fill. When the electron drops from a high energy state to the
lower energy state of the electron hole, light is emitted.
Van Zeijl: “Think of the electrons as water, and the difference between the energy level of a moving electron and that of an electron that has just filled a hole as the height of a waterfall. The height determines the colour of the light that is emitted. For every ten buckets of water that flow down the waterfall, eight or nine are converted into light. The internal efficiency is therefore as much as eighty to ninety per cent.”
However, part of that light does not leave the chip; it is absorbed again soon after, reducing the effi-ciency further, to around thirty to forty per cent. But the expectation is that chips will become much more efficient.
LEDs have been ud in electro-nics since the 1960s. For decades, the chips emitted only weak red light. Since the 1990s, following much experimentation with al-loys, clear blue LEDs have been made using the miconductor materials gallium nitride and indium gallium nitride. The
blue LEDS can be combined with green and red LEDs to produce white light. But white light is usually created by coating the blue LED with phosphors (the are usually rare earth metals) that turn the blue light that is emitted into white light.
How does a light emitting diode work?
PhD student René Poelma rearches the elastic properties of silicons.
Msc Huaiyu Ye has developed a cooling system that us cooling fluid.
>>
17
16PhD student Sima Tarashioon focus on the electronics of the bulb.
The liberation
of
牛虻light
LED bulbs could soon last for
a hundred thousand hours,
believes PhD student Sima
Tarashioon. To achieve this we绿萝需要晒太阳吗
need to know what the life is of
形容很规矩很庄重的词语
all the components of a bulb,
and how they affect each other.
Her work focus on the elec-
tronics of the bulb. Her field is
known as ‘the physics of failure’.
PhD student René Poelma is
interested in the elastic proper-
ties of silicons. LEDs are produ-
ced on a wafer, to which silicon
lens are attached one by one,
by hand. If all the lens could
be attached at the same time, the
cost saving would be huge. But
the lens would have to relea
easily from the mould above.
Poelma’s rearch is geared to
finding the optimum conditions
for this.
Heat
The heat is the limiting factor
in the life of LEDs. Most LEDs
have a passive cooling system:
small metal structures that dis-
sipate the heat. Msc Huaiyu Y e
has developed a cooling system
that us cooling fluid. A few
millilitres of water per cond
flow past the LED through a
very small circular tube. This is
enough to keep the temperature
of the LED at a constant one
hundred degrees Celsius.This
happens automatically. Due
to the pha transition of the
water, from liquid to gas and
back again, the water flows by
itlf. As long as the light is on,
of cour.
Philips wants to produce LED
bulbs that look like miniature
一脉相承
retrofit halogen bulbs. The ma-
jor challenge is to ensure that
the LEDs produce enough light
without overheating. There is
no space in the bulb for cooling
systems. Pan Liu is making fol-
dable chips to hold LEDs. Five
LEDs linked to form an L shape
can be folded into an open cube
胡萝卜先生的长胡子that emits light on all sides. The
open structure allows the heat
that is created to dissipate.
Together with China
The Delft LED rearchers are working
in clo collaboration with fellow
rearchers in China. TU Delft has had
a rearch branch in Beijing since 2011.
The branch has ven PhD students
who are supervid from Delft, and
the plan is to increa this number
to ten in the cour of this year. The
collaboration works in both directions.
For veral months now, Dimes has
houd an office of the Chine State
Key Laboratorium (SKL).
The collaboration ems to be a nsi-
ble move. With a view to saving energy,
China earmarked 22 billion yuan (2.8
billion euros) in 2011 for the promo-
tion of green lighting, primarily LED
lighting.
A lection from the LED rearch at Delft
‘LEDs are chips that
work like a
solar cell in rever’
also important subjects for rearch. (See box
‘A lection from the LED rearch at Delft’.)
Player
With a total of fifteen PhD students and post-
docs, Zhang says his group is one of the major
academic players in Europe. But if you arch
in the scientific literature using the keywords
‘light emitting diode’, you’ll find many other
rearch groups elwhere in Europe (e.g.
Germany, Switzerland and France) that are
publishing much more on the subject. And
Eindhoven University of Technology is scoring
well too in that respect.
Is the Dimes group really such an important
player? “What we’re doing is micro-electronics
and lighting systems integration,” responds
Zhang. “That’s what our rearch focus on,
not on the chip itlf. Y ou’ll e that we lead
the field in Europe in that respect. And many
of our articles still haven’t been publishes yet,
becau the group was only established a few
years ago.”
Prof. Paul Urbach of the Optics rearch
group at the Faculty of Applied Sciences
thinks that TU Delft is a major academic
player in Europe in the field of LED rearch.
He regularly has students and PhD candidates
who are conducting rearch into LEDs,
刘艳华usually in collaboration with Philips. “With
Philips just around the corner, it’s logical that
we’re so big in this field,” he says.
Zhang wants to extend his group in the气功十二法
coming years, and work more cloly with
colleagues from Applied Sciences (including
Prof. Urbach), 3mE and Architecture. He
wants to work with them to t up a Centre
for Solid State Lighting (another name for生命的真相
LEDs).
A long way to go
The group of visitors in Eindhoven has now
reached a dark rearch area where rearchers
are testing whether lamps shine evenly in all
directions. Despite all the fascinating possi-
bilities, Philips’ efforts, as far as the consumer
market is concerned, remain largely focud
for the time being on LED bulbs that can be
screwed into a socket. One such bulb - the L
bulb - was recently tested here.
Philips developed the L bulb to replace the
sixty- watt incandescent bulb. In 2011 it won
the company ten million dollars (the Bright
Tomorrow Lighting Prize), a prize awarded
by the U.S. Department of Energy. The LED
bulb consumes ten watts and should last for
twenty thousand hours.
PhD student René Poelma has a similar LED
bulb at home, he says. “It gives very fine light.
Very diffu. Y ou can’t tell that it’s an LED
bulb rather than an incandescent bulb.”
Y et Poelma doubts whether we are on the eve
of an LED revolution. “Personally, I wouldn’t
have bought the bulb. I think it’s still too ex-
pensive. In my view there’s a long way to go
before they’re interesting to consumers.”
The award-winning Philips bulb still costs
sixty euros. But according to Zhang, there are
already high-quality LED bulbs on sale for
much less than this. And very rapid advances
are being made. “In China you can already
buy a good bulb for ten euros.”
Dr Henk van Zeijl (Dimes).
Prof. Kouchi Zhang: “Retrofit is actually very stupid.”
Prof. Paul Urbach: “TU Delft is a major academic player in Europe.”
>>
19 18
Below is given annual work summary, do not need friends can download after editor deleted Welcome to visit again
XXXX annual work summary
Dear every leader, colleagues:
Look back end of XXXX, XXXX years of work, have the joy of success in your work, have a collaboration with colleagues, working hard, also have disappointed when encountered difficulties and tbacks. Imperceptible in ten and orderly to be over a year, a year, under the loving care and guidance of the leadership of the company, under the support and help of colleagues, through their own efforts, various aspects have made certain progress, better to complete the job. For better work, sum up experience and lessons, will now work a brief summary.
To continuously strengthen learning, improve their comprehensive quality. With good comprehensive quality is the precondition of completes the labor of duty and conditions. A year always put learning in the important position, trying to improve their comprehensive quality. Continuous learning professional skills, learn from surrounding colleagues with rich work experience, equip themlves with knowledge, the expanded aspect of knowledge, efforts to improve their comprehensive quality.
The cond Do best, strictly perform their responsibilities. Set up the company, to maximize the customer to the satisfaction of the company's products, do a good job in technical rvices and product promotion to the company. And collected on the properties of the products of the company, in order to make improvement in time, make the products better meet the using demand of the scene.
Three to learn to be good at communication, coordinating assistance. On‐site technical rvice personnel should not only have strong professional technology, should also have good communication ability, a lot of a product due to improper operation to appear problem, but often not customers reflect the quality of no, so this time we need to find out the crux, and customer communication, standardized operation, to avoid customer's mistrust of the products and even the damage of the company's image. Some experiences in the past work, mentality is very important in the work, work to have passion, keep the smile of sunshine, can clo the distance between people, easy to communicate with the customer. Do better in the daily work to communicate with customers and achieve customer satisfaction, excellent technical rvice every time, on behalf of the customer on our products much a understanding and trust.
Fourth, we need to continue to learn professional knowledge, do practical grasp skilled operation. Over the past year, through continuous learning and fumble, studied the gas generation, collection and methods, gradually familiar with and master the company introduced the working principle, operation method of gas machine. With the help of the department leaders and colleagues, familiar with and master the launch of the division principle, debugging method of the control system, and to wuhan Chen Guchong garbage power plant of gas machine control system transformation, learn to d
ebug, accumulated some experience. All in all, over the past year, did some work, have also made some achievements, but the results can only reprent the past, there are some problems to work, can't meet the higher requirements. In the future work, I must develop the onelf advantage, lack of correct, foster strengths and circumvent weakness, for greater achievements. Looking forward to XXXX years of work, I'll be more efforts, constant progress in their jobs, make greater achievements. Every year I have progress, the growth of believe will get greater returns, I will my biggest contribution to the development of the company, believe in
yourlf do better next year!
I wish you all work study progress in the year to come.
