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Reference Number EP/H004602/1
Title Ultra energy efficient III-nitride/polymer hybrid white LEDs using nanotechnology
Status Completed
Energy Categories ENERGY EFFICIENCY(Residential and commercial) 100%;
Research Types Basic and strategic applied research 100%
Science and Technology Fields ENGINEERING AND TECHNOLOGY (Electrical and Electronic Engineering) 100%
UKERC Cross Cutting Characterisation Not Cross-cutting 100%
Principal Investigator Dr T Wang
No email address given
Electronic and Electrical Engineering
University of Sheffield
Award Type Standard
Funding Source EPSRC
Start Date 01 April 2010
End Date 31 March 2014
Duration 48 months
Total Grant Value £389,462
Industrial Sectors No relevance to Underpinning Sectors
Region Yorkshire & Humberside
Programme Information & Communication Technology, Physical Sciences
Investigators Principal Investigator Dr T Wang , Electronic and Electrical Engineering, University of Sheffield (100.000%)
Web Site
Objectives Linked to grant EP/H004157/1
Abstract The last decade has seen dramatic advances in the development of III-nitride light emitters, whose emergence is significantly changing many aspects of our lives. Materials from the III-nitride family can emit light over the complete visible spectrum and a major part of the ultraviolet (UV) and are ideally suited for white light sources. Developments in solid-state lighting are occurring at pace and will lead to near-ultimate lighting sources, likely to be based on III-nitride materials. This will result in a fundamental change in the concept of illumination and has the potential to lead to massive savings in energy, estimated to be equivalent to $112 billion by the year 2020. Such increases in efficiency are increasingly important due to the growing world-wide energy-crisis and threat ofglobal warming.Currently, there are three main approaches for the fabrication of white light emitting diodes (LEDs) needed for solid-state lighting: (1) a package of three LED chips each emitting at a different wavelength (red, green and blue, respectively); (2) a combination of a blue (460 nm) LED with a yellow phosphor pumped by blue light from the LED; (3) a single chip emitting UV light whichis absorbed by three phosphors (red, green and blue) and reemitted as a broad spectrum of white light. The first method is ideal for achieving a true white light source, but it is extremely difficult to balance the electro-luminescence intensities of these different colours and there exist a number of fundamental challenges related to the different requirements of the individual LEDs. The performance of current UV-LEDs is far below blue-LEDs and presents a major limitation to the third route. As a result the "blue LED+ phosphor" approach is maintaining its strong lead for the fabrication of white LEDs with several commercial successes. However, the most promising commercially available white LEDs are based on blue epiwafers with the highest crystal quality, which are thus extremely expensive. This raises the price and thus limits their applications in general illumination. Further development of the technology is also still faced with problems, which are the driving force behind the new type of LED proposed here. We aim to develop a hybrid nanotechnology delivering a new type of ultra high energy efficient white-LED without need for the premium price blue epiwafers.Thetechnologies to be hybridised are arrays of semiconductor nano-rods, with dimensions on the scale of 100s of nanometres, metal nano-particles and polymers. Building on our work demonstrating efficient light emission from conjugated polymers we will optimise these materials for converting blue light to yellow. The new polymers will be used to fill the spaces between nanorods prepared in GaN-basedLED structures, maximising the contact between the blue light source and the yellow emitter. Blending silver nano-particles into the polymer will be used to further improve optical performance as a result of a coupling effect between the metal and semiconductor. Relatively thick capping layers usually limit the strength of this effect but the close contact between the polymer/metal blend and theside-walls of the nano-rods enables us to get close to the full benefit.This work will combine the existing strengths at the Sheffield in III-nitride device fabrication and characterisation of III-nitride emitters with those at Strathclyde in polymer chemistry, fundamental optical studies ofIII-nitrides and characterization of nanostructures, including metal nanoparticles and semiconductors. Thiscombined effort aims to achieve an improved understanding of the fundamental issues in the optical emission processes mentioned above and to optimise fabrication processes of hybrid III-nitride/polymer white LEDs. It will lead to the demonstration of next generation white-LEDs suitable for replacement of conventional light sources in terms of cost and luminous efficacy
Publications (none)
Final Report (none)
Added to Database 14/09/09