Philips novel method accelerates progress in OLED lighting efficiency

March 15, 2010

Eindhoven, The Netherlands - Scientists from Philips Research and the Eindhoven University of Technology (TUe) have developed a novel method for accurately measuring the active layer in organic light-emitting diode (OLED) lighting. This is an important step forward for OLED device optimization and efficiency that is determined by the position of the very narrow zone in which the light is generated. The findings were published online in Nature Photonics on Sunday 14 March.
 

In the past five years OLEDs have emerged as a promising option for energy-efficient solid-state-lighting. OLEDs can cover large areas; they are extremely thin and can be made on substrates of virtually any shape. This high level of flexibility in terms of design and application makes them highly appealing to lighting designers, manufacturers and consumers.
 

Unlike incandescent bulbs, which generate light by passing electricity through a wire, or fluorescent lamps, which pass current through a gas, OLED lighting works by passing electricity through one or more incredibly thin layers of organic semiconductors. These layers are sandwiched between two electrodes. The whole “sandwich” is deposited onto a supporting sheet of glass or other transparent material. When current is applied to the electrodes it flows through the organic film and the film emits light. Using different materials in the films makes it possible for the OLEDs to emit differently colored light, and using a combination of materials pleasant white light is emitted.

 

Measuring efficiency
The novel method has been developed by PhD students Siebe van Mensfoort and Marco Carvelli from the Eindhoven University of Technology working for the Dutch Nano Technology program 

 

NanoNed and the Dutch Polymer Institute, as well as researchers from Philips Research (Aachen and Eindhoven). "There are many factors that influence the efficiency, or light out-coupling efficiency. Not all the light reaches our eyes, as some of it is trapped and absorbed in the OLED, particularly when it is formed close to the electrodes. In the most efficient OLEDs the light comes nicely from the center. Simply put, we have provided the microscope through which we can see whether we are able to perfectly realize that goal,” Marco Carvelli explains.

Initially blue OLEDs were looked at because of the relatively simple single-layer structure. "You need to know the light emission profile with a high degree of certitude to calculate the light out-coupling efficiency, which is the most important efficiency loss factor in state-of-the-art OLEDs,” Reinder Coehoorn, Research Fellow, indicates. “We are very proud of the fact that Nature Photonics has picked up the paper and are looking forward to expanding the analysis to multilayer devices, for which a more structured profile is expected."

This is a great achievement and it demonstrates the good progress we are making in understanding OLEDs,” says Dietrich Bertram, manager of the OLED Lighting business center at Philips Lighting.“The insights from this and other research activities are important contributions to further improving the performance of our Lumiblade OLED lighting devices and to secure our leading position in OLED lighting,” he continues.


Developing OLEDs

In 2009, Philips was the first to introduce OLEDs for lighting, selling Experience Kits under the trade name Lumiblade™. Philips continues to further develop OLED technology for lighting applications with experts from leading industrial and academic organizations in projects such as Aeviom, Fast2light, OLLA, OLED100.eu, TOPAS 2012, OLED3D and more. Recently the OLED100.eu project received the - Best ICT for Energy Efficiency Project Award from the European Commission.

 

 


More information:

 

The publication “Measuring the light emission profile in organic light-emitting diodes with nanometre spatial resolution” by van Mensfoort et al. can be found at http://www.nature.com/nphoton/journal/vaop/ncurrent/abs/nphoton.2010.32.html

 

Download high-resolution pictures:

+ OLED

For further information, please contact:

Hans Driessen – Philips Research
Mob: +31 610610417
Email: hans.driessen@philips.com
 .

About Royal Philips Electronics

Royal Philips Electronics of the Netherlands (NYSE: PHG, AEX: PHI) is a diversified health and well-being company, focused on improving people’s lives through timely innovations. As a world leader in healthcare, lifestyle and lighting, Philips integrates technologies and design into people-centric solutions, based on fundamental customer insights and the brand promise of “sense and simplicity”. Headquartered in the Netherlands, Philips employs more than 116,000 employees in more than 60 countries worldwide. With sales of EUR 23 billion in 2009, the company is a market leader in cardiac care, acute care and home healthcare, energy efficient lighting solutions and new lighting applications, as well as lifestyle products for personal well-being and pleasure with strong leadership positions in flat TV, male shaving and grooming, portable entertainment and oral healthcare. News from Philips is located at www.philips.com/newscenter.

 

.