Organic light-emitting diodes

The 2014 Nobel Prize in Physics was awarded “for the invention of efficient blue light-emitting diodes (LEDs) which has enabled bright and energy-saving white light sources” [1, 2, 3], setting a clear target to mankind: energy-efficient and environmental-friendly light sources [4]. The first organic LED (OLED) was reported in 1987 by a team at Kodak [5]. This publication, cited to date more than 10,000 times, stipulated the entire field of organic electronics. Shortly afterward, a polymer LED (PLED) was demonstrated [6], 474paving the way for flexible lighting applications [7]. Nowadays, OLEDs are successfully used in displays of mobile phones and televisions: In 2008, Samsung announced a flexible display that was only 50µm thick [8], about half the thickness of a sheet of paper. A prototype of an OLED display for the automotive market was presented recently by Continental [9]: In OLED displays, black pixels are completely switched off, allowing the driver’s eye to adapt better to the darkness. Contrary to liquid crystal displays (LCDs), OLED screens do not require backlight illumination, yielding exceptionally good contrast ratios and reduced power consumption. OLED displays also provide viewing angles and response times superior to LCDs and are, in general, thinner and lighter. Last but not least, many organic materials can be printed from solution, enabling cost-effective large-scale manufacturing on mechanically flexible films.