Thorn Lighting, based in Spennymoor, UK, is leading a project to develop organic light-emitting diode (OLED) materials and efficient device structures for large area lighting applications.
Partners in the project are the University of Durham (Photonics Materials Institute) and Cambridge Display Technology (CDT), with the UK government's Department for Innovation, Universities and Skills (DIUS – see below) providing a maximum funding of £1.6m over three years. The total initial funding amounts to £3.3m.
Geoff Williams, Thorn's OLED Group Leader, said: "The materials we are hoping to develop will give high brightness, high efficiency white light, which could replace general-purpose lighting."
However, the challenge does not only exist for the materials and devices. "The Thorn team will strive to design new Sigma 6 manufacturing and quality control processes appropriate for this emerging technology,” said Williams.
Under the terms of the grant, CDT through its Sumation joint venture will provide significant knowledge and experience in the field of light-emitting conjugated polymers as well as delivering polymer-based OLED materials, device architectures and testing.
Durham University has developed one of the most important academic alliances between physicists and chemists in Europe, having unique facilities for studying energy transfer mechanisms in both polymer materials and device structures.
Wafer-thin OLED panels are one of the key technologies touted to displace conventional light sources, such as fluorescent and incandescent lamps. OLEDs offer the potential for large-area white lighting. The materials can be printed onto either solid or flexible glass or plastic substrates with long life (20,000 hours), reduced energy consumption and less waste (1kg of material will coat 10,000,000m2 of lighting area). Electrical efficiency should be close to fluorescent tubes.
"The target is 50 lumens per watt in four to five years, with a colour rendering index (CRI) better than standard fluorescent lamps," said Williams. "The eventual target is 150-200 lm/W. In 2015 we will be near this level and by 2020 OLED lighting will be the first choice."
The Zumtobel Group, Thorn’s parent company, follows a strategy including both organic and inorganic LED devices. Its subsidiaries Ledon and Lexedis are focusing on inorganic LED technology, and the R&D activities concerning organics are currently centralized in the UK OLED project.
Andreas Ludwig, CEO of the Zumtobel Group, emphasizes the importance of the tripartite project: "The long-term expectation for professional lighting must incorporate organic and inorganic LEDs. Securing this UK Government grant for the development and commercialization of OLEDs further expands our opportunities in solid-state lighting. As a result, we are now strongly positioned in this challenging area of technology with substantial long-term potential."
The project will allow Thorn to challenge traditional lighting philosophies, while pointing the way towards environmentally friendly artificial lighting based on low voltage DC devices and sustainable renewable energy sources.
Department for Innovation, Universities and Skills (DIUS)
The new Department for Innovation, Universities and Skills (DIUS) brings together functions of the Office of Science and Innovation from the former Department of Trade and Industry, with further and higher education and skills, previously part of the Department for Education and Skills. It aims to make Britain one of the best places in the world for science, research and innovation.
OLED technology
An organic light-emitting diode (OLED) is a solid-state lighting device composed of thin films of organic carbon-based molecules or polymers that create light when excited by the application of electricity – similar to electroluminescent lighting. They are already found in mobile phone displays and MP3 players.
To create the device scientists build up ultra-thin layers of compounds (hundreds of times smaller than a human hair), which depending upon the type of emissive material used, can be almost any colour, including white.
This project’s aim to reduce the number of organic layers to one at the most two, an unique challenge, but one which is already generating results. The power supply is low voltage.
The lightweight material can be printed onto a solid or flexible, glass or plastic, substrate base and has the advantage of being viewed from wide angles. With inkjet technology OLEDs can be sprayed onto large, thin panels, relatively cheaply.
Before OLEDs become a reality though, scientists need to overcome issues such as uniformity, life and moisture, oxygen and UV degradation. With polymers encapsulated by glass these issues are already resolved. However, when the substrate becomes flexible and oxygen migration becomes a problem, the reactive metal cathode being the most sensitive to degradation in life. OLEDS can be printed over large areas, unlike inorganic LEDs, which are used more as point light sources.
