EPSRC Gives Research Grant For Blue Emitting LEEC and OLEDs
Dr E Zysman-Colman
of the University of St Andrews has been awarded a grant of GBP 348,060 from the Engineering and Physical Sciences Research Council (EPSRC) to investigate how to produce higher performance deep blue emitting OLEDs. EPSRC is the main UK government agency for funding research and training in engineering and the physical sciences, investing more than £800 million a year in a broad range of subjects – from mathematics to materials science, and from information technology to structural engineering. An excerpt from the grant application follows;
Whereas inorganic LED and organic or polymer OLED lighting is now the state of the art in artificial lighting, their high cost and small active surface area are still barriers to wide adoption. In fact, for large surface area outdoor lighting applications, low-pressure sodium lamps are still the technology of first choice. Within this context, there is an urgent need to find alternative artificial lighting technologies that are of lower production cost, more energy efficient, colour tunable and can be used in environments not currently accessible to current LED and OLED technologies. It is implicit that in a similar manner to OLEDs, such a new lighting technology would have applications in visual displays, telecommunication and sensors.
Organometallic complexes capable of harnessing light and/or electrical current and transforming such energy into useful work are at the heart of many important applications. An application that is of particular interest to my research group is energy-efficient visual displays and flat panel lighting based on either a phosphorescent light-emitting electrochemical cell (LEEC) architecture or an OLED architecture. Currently, most ionic transition metal complex-based (iTMC) LEECs rely on the use of a charged iridium(III) complex as the luminophoric material. These complexes can be readily solution processed. Iridium complexes phosphoresce and thus the maximum photoluminescence quantum efficiency (PLQY) theoretically attainable is unity. The external quantum efficiency (EQE) of a LEEC device has been found to scale proportionately to the solid-state PLQY and as such bright devices are possible. Despite the advantages listed above, LEECs incorporating iTMCs have several weaknesses: (i) low EQE; (ii) limited stability of the device and (iv) colour quality, particularly with reference to blue light emission.
This grant proposal targets the development blue-emitting iridium(III) cationic complexes that will act as a luminophoric material in both LEEC and OLED devices. The two main goals are: 1. to obtain a LEEC that emits brightly in the blue region of the spectrum and that is stable over thousands of hours and that can quickly illuminate upon the application of an external voltage; to produce higher performance deep blue emitting OLEDs.