Power consumption - Page 39

Cuttlefish are able to change their skin color quickly. Now scientists from MIT are working to create displays that are extremely efficient - using less than one-hundredth the power of today's TVs. Cuttlefish use chemicals to change the space between membranes on their skin. The researchers have created an artificial electrical system that controls spacing between layers in their display, thus changing the color.

The prototype display is several inches across, and only one micron thick - inside there are around 20 layers of polystrene and responsive poly-2 vinyl. The poly-2 vinyl expands as the voltage increases, becoming thicker, and reflecting longer wavelengths of light. Without electricity it is clear.

Physicists from the Technical University of Dresden, together with Novaled has developed a new white OLEDs with efficiency of 90lm/w. They have used a new emission layer design and improved light outcoupling concepts. In fact, with special 3D outcoupling measures, they have achieved 124 lm/W.

Both values
were determined in an integrating sphere with blocked substrate edges,
only taking the light into account that is emitted to the forward
hemisphere, CIE color coordinates are (0.41/0.49). An in depth article
is published in today’s highly esteemed research journal ‘nature’.

The potential of the devices is obvious when one considers that even at
the very high brightness of 5,000 cd/m² a power
efficiency of 74 lm/W is obtained, comments Prof. Karl Leo, Director of the Institute of Applied Photophysics (IAPP, TU Dresden). Thus high-intensity illuminations at very high efficiencies are
possible as well.

Novaled, Fraunhofer IPMS and Optrex Europe developed a new, unique PMOLED driver. They have implemented an innovative MLA scheme called SELA (Summed Equiline Addressing). Basically, instead of driving using a single-line addressing scheme, the SELA allows parallel driving of multiple rows, thus preventing high current amplitudes.

Basically this means that we get higher lifetime, better resolution and better efficiency in the OLED display. The driver is specified for operations between -40°C and +125°C, exhibits an OLED drive voltage up to 25 V, and a column source current up to 2 mA. In particular the latter can currently not be fulfilled by any commercial available PM OLED driver.

In addition to the innovative addressing concept and the new OLED MLA driver, a high temperature stable and long-living orange emitting PIN OLED layer stack was developed by Novaled AG. In automotive applications high reliability at 85°C
operational temperature and highly stable brightness (often only 20% reduction over lifetime is allowed) is required. The newly developed OLED stack offers an operating lifetime of currently 5.300 hours at 85°C and 20% brightness drop at an initial brightness of 600 cd/m².

During the Light Fair in Jacob K Javits Convention Center, New York, WAC lighting is showing some beautiful OLED fixture prototypes - one mini-chandelier, and one wall sconce. They sent us a lot of info, photos and videos of these lamps...

The OLED wall sconce uses 6 color-changeable, 3" OLEDs:

One of the great things about OLEDs is that they are power efficient. Interestingly, for OLED displays, the application makes a great impact on the power consumption. The more bright-pixels, the more power is consumed.

If OLEDs are adopted widely, it will start to make sense to design software in such a way as to maximize power efficiency. This will be very useful for mobile devices - be it phones or laptops.

Here are a few ideas that can be used to maximize battery life with an OLED:

• Use a black or dark background.


• Hide parts of the application that is not used - like menus, for example. The less displayed, the better.


• Use only a part of the screen: in OLED laptops, it will make sense to allow for modes in which not all the screen is used. For example - use only half the width, to save half the energy.


• Dim the background: if you have a window that is not in focus, for example, it can be dimmed. This also saves power.


• Instead of just a screensaver after several minutes (which will actually save power if mostly black), one can have the display slowly dim after a few seconds.


• Use color wisely: to show white on an OLED, you'll have to emit light from 3 different pixels (Red+Green+Blue). To show true red, only one pixel is required. This basically means that showing a colored font will be more efficient than a white one. Showing red is more efficient than orange, too.


• Use a flickering display: This might be a bit drastic - but perhaps we can have a mode in which each pixel is turned off at half the time. It'll save half the energy. An "interlaced" display is a similar idea.

So, okay, some of these can be annoying, and have only a slight effect. But these may prove a great option for long battery life. If I'm taking a digital camera on a long trek for a few days, I might be happy to be able to take more photos in exchange for a red menu on the OLED monitor.

Do you have other ideas to save power? Please comment and share!

A research group from the Kanazawa
Institute of Technology in Japan succeeded in making an green phospor-based OLED achieving a very high
light-emitting efficiency of 210lm/W (56.9% more efficient than existing OLEDs).

The OLED is a bottom-emission type on a 0.7mm-thick glass plate. 

The material for the device's light-emitting layer is a host material called "CBP" added with an iridium complex, "Ir(ppy)₃." Its light emission peak lies in the range of wavelengths between 500 and 550nm, which corresponds to green color.

When emitting light at a luminance of 10cd/m², it has a
light-emitting efficiency of 210lm/W and a light-extraction efficiency
of 56.9%. On the other hand, when emitting light without the
high-refractive glass plate, its light-emitting efficiency is only
94.3lm/W. This means the glass plate boosted the light-extraction
efficiency by 2.3 times.

The nice chaps at the OLED100.eu project sent me this nice EuroNews video, explaining OLED lighting and the OLED100.eu project. It includes some nice ideas on flexible or transparent OLED lighting.

I really liked the OLED chess set featured in this film. Also the futuristic OLED kitchen has some nice ideas.

Panasonic is working on OLED lighting panels, using printing methods. They prototypes a high efficiency panel at Printable Electronics 2009.

The OLED lighting panel features a luminance efficiency of 40lm/W and a CRI (color rendering index) value of 95. The external quantum efficiency is 36.1%, and the half-life of the luminance exceeds 20,000 hours when the initial luminance is 1,000cd/m^2.

Read more at TechOn

Merck is a global pharmaceutical and chemical company based in Germany. The company designs, develops and manufactures a wide range of specialised materials including high performance light emitting materials for OLEDs. The OLED business belongs to Mercks' Liquid-Crystal (LC) unit.

I managed to conduct an interview with Dr. Udo Heider, the VP of the LC business unit at Merck (it's called the LC/OLED unit) about their OLED program.

Q: Hello Dr. Heider, and thank you for this interview. Can you describe your range of OLED products in more detail? Are you just into OLED materials, or other IPs as well?

There are reports that the new OQO Model 02+ UMPC OLED display is not as efficient as you'd expect. The PC is not available yet, but there are some pre-production models around, and someone tried to see how much power the display takes.

OQO Model 02+ photo

As far as I understand, they tested the  power-consumption of the entire PC - and it's not so good - but it may be the fault of other components and not just the display.