"Green" OLED-Displays – High Image Quality at Low Energy

They are regarded as displays of the future – organic light emitting diode-displays – called OLED-displays in short. This technology is already applied in mobile phones, MP3-players and digital cameras.

It is based on the phenomenon that certain organic materials emit light, when fed by an electric current. The new OLED-displays can be thin as a film and just as flexible. Furthermore they have a wide viewing angle and display videos perfectly. A further benefit is that these displays need little energy.

“Compared to the present standard, more than the half of the energy can be saved for the OLED-display-operation”, Chihao Xu stated. “Especially for mobile applications, saving of energy is reasonable” explains the professor. The display consumes most of the energy in mobile devices such as the mobile phone. Especially by charging and discharging a lot of energy gets lost”. The scientists from Saarbrücken are searching for avoiding this high power loss.

This shall be achieved by the new driving scheme SQC (State dependent Charge controlled Driving) for actuating passive matrix OLED-displays. This scheme will substantially reduce the power consumption especially for high resolution displays, and will naturally guarantee the known excellent image quality of an OLED-display.

The microelectronics group of Saarland University is worldwide leading in the field of the OLED-driving. Within the CARO-project (CAR OLED) Chihao Xu and his team together with partners from science and industry, such as Optrex Europe GmbH and the Fraunhofer Institute for Photonic Microsystems (PIMS), participated in the development of a new driver chip, which shall be implemented in OLED-displays for cars. In this project, a new multi-line addressing scheme (“SELA”, Summed Equi-Line-Addressing) is used. This method significantly increases the lifetime of OLEDs and makes them more attractive for high performance applications.

“OLEDs have many advantages, particularly in cars. The displays react immediately also at very low temperatures. Besides, dark pixels are really black and differ only slightly from the surroundings in the cockpit. This leads to an appearance more beautiful and more splendid”, explains Chihao Xu. The driver chip from the CARO-project, realized by the Fraunhofer IPMS, is designed in such a versatile manner that also SQC can be implemented.

“Also with regard to cars, saving of energy is an important matter” says professor Xu. “Therefore it is consequent to research on the combination of this power-efficient driving scheme and the Summed-Equi-Line-Addressing and to develop a marketable demonstrator”.

Now, the microelectronics group of Saarbrücken will together with Optrex Europe GmbH and further partners continue to push on the efficient control of passive matrix-OLED-displays, so that they can gain more interest especially in high-grade applications, like e.g. in cars.

The research association with the name CARO is one of the research associations, which is promoted within the scope of the initiative “OLED 2015” (phase 1), set up by the German Ministry for Education and Research in 2006. The participating CARO-partners thank the ministry for the financial assistance of the individual projects with the project codes 01BD 0680-0688; the project will expire in autumn.

For further information please contact:

Prof. Dr. Chihao Xu
Phone: +49 681/302-4305
chihao.xu@lme.uni-saarland.de
Universität des Saarlandes
Lehrstuhl für Mikroelektronik
Campus
66123 Saarbrücken
Dr. Jürgen Wahl
Phone: +49 6073 721 200
Juergen.Wahl@Optrex.de
Optrex Europe GmbH
Seligenstädter Str. 40
64832 Babenhausen
Ines Schedwill
Phone: +49 351 8823-238
info@ipms.fraunhofer.de
Fraunhofer-Institut für Photonische Mikrosysteme
Maria-Reiche-Str. 2
01109 Dresden