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Posted on June 18, 2007 by  & 

Who is Winning With OLED Lighting?

At the recent IDTechEx Printed Electronics Europe conference in Cambridge, Dr Peter Visser of Philips and the pan European OLLA project reviewed the work of OLLA. The acronym "OLLA" stands for "high brightness organic light emitting diodes for ICT & lighting applications". The program involves 24 partners from 8 European countries, among which 10 from industry, 7 academia and also 7 universities, including the EC financial support. It represents a total R&D budget of around 20 million Euros.
The project officially started on October 1st 2004, but work on the project had been started more than one year before that date, in order to prepare the project plan for submitting it to the call for proposals by the European Commission. The original idea for the project came from Philips Lighting, which wanted to investigate the potential of the OLED technology for lighting applications.
Organic LEDs, even on glass, are in general an interesting light source as they are flat sources, give a homogeneous light over an area, are potentially very energy efficient, and there are options to have many colours within one device. Glass substrates are used and the focus is performance. The project ends in 2008.
The needs for lighting are:
High volume, cost sensitive market with multiple segments
  • General lighting (illumination)
  • General lighting (luminance)
  • Automotive lighting
  • Special lighting
  • General spec: ~10,000 hours to 80% initial brightness
  • Shelf life general ~10 years
  • Depends on market segment (general >10 lm/W)
Color & light quality
  • CRI >80 for illumination
  • All colours for luminance
Source: Olla
The potential advantages of OLED lighting were cited as:
  • Large area diffuse light source
  • Thin, flat, lightweight
  • Form freedom in design
  • Fast switch-on; fully dimmable
  • Many colors, incl. whites
  • Robust source (no wires inside)
  • Transparent, mirror-like, black or white appearance
  • Low voltage technology
  • Potentially high efficiency
  • "Green" product (energy efficient, recyclable)
  • Potentially cheap fabrication
The challenges for OLED lighting in order to compete with existing light sources were given as:
  • High Luminance: Lighting applications needs at least 1,000 Cd/m² brightness
  • Long Lifetime: Long operation and shelf lifetime is necessary
  • High Efficiency: At least 30 lm/W in WHITE
  • Good Homogeneity: Especially on large areas applications
  • High CRI at high brightness: > 80 for direct lighting applications
  • Very low costs
Source: Olla
However, IDTechEx notes that flexible OLEDs will also create new applications for lighting that can not be addressed by existing solutions. In this respect it will compete with the improving ac electroluminescent flexible lighting by offering better colors and lower voltages.
IDTechEx notes that another candidate for laminar lighting is inorganic LEDs. These are very successful in torches, car rear lights, traffic lights etc. but they give harsh light from point sources, so there is a race to improve on this. However, most believe that the provision of lighting of many colours and tints on flexible substrates will best be provided by improving the performance, life, wide area fabrication and substrates of OLEDs. Peter Visser sees the timelines as follows:
For now, almost all OLEDs employ expensive, rare metals in both the organic layer and the indium tin oxide transparent electrode but the first priority is usually to juggle the rare elements in the organic layer to improve performance and replace the indium with common materials. For example, polythiophene transparent electrodes have been successfully employed. Drive circuits and printing technology are being improved with gravure looking particularly promising.
The current state of the art is:
  • 64 lm/W at 1,000 cd/m² small size
  • Optical enhancement
  • 10,000 hours lifetime (50%)
In March 2007, Konica Minolta and GE announced a joint venture in the USA to commercialise OLED lighting within three years.
Yamagata University, Prof. Kido
  • 48lm/W at 1,000 cd/m²
  • No optical enhancement
  • Lifetime not disclosed
UDC (3)
  • 23.8lm/W at 500 cd/m²
  • With optical enhancement (back-reflector)
  • Lifetime not available
  • 32lm/W at 1,000 cd/m²
  • With optical enhancement
  • >20,000 hours lifetime (50%)
  • ITO free OLED device with same performance than with ITO (4)
  • MS2: 25 lm/W
Source: Olla
As with OLED displays, there are two types of OLED used in lighting:
Source: Olla
Source: Olla
OLED lights 150 mm X 150 mm have been made.
Source: Olla
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