Ultra energy efficient III-nitride/polymer hybrid white LEDs using nanotechnology

Lead Research Organisation: University of Sheffield
Department Name: Electronic and Electrical Engineering

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 of global 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 which is 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. The technologies 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-based LED 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 the side-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 of III-nitrides and characterization of nanostructures, including metal nanoparticles and semiconductors. This combined 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

10 25 50
 
Description Development of nano-patterning methods to fabricate high quality arrays of III-nitride pillars.

Optical investigation of InGaN/GaN based nano-rod arrays

Optimisation of polymers for blue-yellow down conversion, demonstrating improvements in terms of self-absorption, conversion efficiency and quenching.

Demonstration of successful energy transfer between nano-pillar InGaN MQWs and proximal polymer

Demonstration of additional improvement in efficiency due to coupling between the nano-pillar InGaN MQW and silver nanoparticles within the proximal polymer

Combination of the above to fabricate hybrid III-nitride/polymer white LEDs

Demonstration of first electrically injected hybrid III-nitrides/F8BT polymers white LEDs with a high efficient non-radiative energy transfer
Exploitation Route 1) joint publications and joint grant applications and technology transfer
2) The technologies developed through the project have been highlighted at Industrial event organized by Professor Tao Wang, on 10 January 2017, Sheffield. This event has attracted more than 10 semiconductor companies across the UK, where the CEOs or technical directors attended.
Sectors Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment,Healthcare

 
Description These findings have been commercialized, and have been transferred to the university spinout. These findings also significantly contributed to the funds raise of the spinout, £1.8M in 2012, and then £1.9M in 2014
First Year Of Impact 2010
Sector Digital/Communication/Information Technologies (including Software),Education,Electronics,Energy,Environment
Impact Types Societal,Economic

 
Description A MOU was signed between the Unversity of Sheffield and Universiti Sains Malaysia in order to initiate A Networking On Nitrides Semiconductor Optoelectronics And Electronics 
Organisation University of Science Malaysia
Country Malaysia 
Sector Academic/University 
PI Contribution The Sheffield GaN center led by Professor Tao Wang has established an internationally recognized reputation in the field of III-nitride opto-electronics, ranging from epitaxial growth, through material characterization to device fabrication.
Collaborator Contribution The team at Universiti Sains Malaysia has good experience in technology commercializing. Therefore, both team aims at enhancing academic exchange and cooperation in this field
Impact The MOU was just signed several weeks ago. Hopefully, we will have results soon
Start Year 2019
 
Title DBR Enhanced micro-LEDs 
Description DBR Enhanced micro-LEDs 
IP Reference UK Patent Application No. 1910352.2, 
Protection Patent application published
Year Protection Granted 2019
Licensed Commercial In Confidence
Impact Awaiting impact
 
Title LED arrays 
Description A new method for the growth of micro-LED arrays 
IP Reference GB1816455.8 
Protection Patent application published
Year Protection Granted 2018
Licensed Commercial In Confidence
Impact Major impact on developing III-nitride based microLEDs for micro-display, Ultra-fast visible light communications, AR/VR
 
Title Light emitting diodes 
Description Fabrication of GaN based nano-emitters 
IP Reference GB0910619.6 
Protection Patent application published
Year Protection Granted 2010
Licensed Yes
Impact Contribute to funds-raise of the spinout company
 
Title Semiconductor devices and fabrication methods 
Description Fabrication of novel GaN nanostructures 
IP Reference GB2487917 
Protection Patent application published
Year Protection Granted 2011
Licensed Yes
Impact Contribute to the funds-raise of the spinout
 
Title multiple-colored Micro-LEDs 
Description multiple-colored Micro-LEDs 
IP Reference UK Patent Application No. 1910348.0, 19th July 2019 
Protection Patent application published
Year Protection Granted 2019
Licensed Commercial In Confidence
Impact awaiting impact
 
Company Name EPIPIX LIMITED 
Description Dedicate to manufacturing III-nitride opto-electronics 
Year Established 2020 
Impact This spinout is just established a few weeks ago. It is expected to have a major impact in a wide range of industrial field, such as display, AI, communications, etc
 
Description 2020 Industrial open day 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact It aims to establish new collaboration with industry and further strengthen existing collaboration with industry, and to support the UK advanced manufacturing.
Year(s) Of Engagement Activity 2020
 
Description BJ: 2019 UKNC Conference, Glasgow, UK, 9-10th January 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Present the latest results on developing Nonpolar a-plane (11-20) InGaN-based light-emitting diodes grown on micro-rod templates
Year(s) Of Engagement Activity 2019
 
Description LJ: 2019 UKNC Conference, Glasgow, UK, 9-10th January 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact present latest report on developing Monolithic multiple colour emission from InGaN grown on patterned non-polar GaN
Year(s) Of Engagement Activity 2019
 
Description TW: 2019 Industrial open day 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact It aims to establish new collaboration with industry and further strengthen existing collaboration with industry, and to support the UK advanced manufacturing.
Year(s) Of Engagement Activity 2019
 
Description XY: 13th International Conference on Nitride Semiconductors 2019 (ICNS-13), Bellevue, Washington, USA, 7th-12th July 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact The presentation report on design and then fabrication of Semi-Polar (11-22) GaN for Green Emitters on Si Substrates. It is expected to draw strong attention from industry.
Year(s) Of Engagement Activity 2019
 
Description XY: 2019 UKNC Conference, Glasgow, UK, 9-10th January 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Present latest report on developing semi-polar (11-22) GaN for green emitters on Si substrates
Year(s) Of Engagement Activity 2019
 
Description XZ: UKNC Annual Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact The presentation reported out latest results on developing semi-polar InGaN-based green LEDs with super-lattice on patterned silicon. It is expected to draw strong attention from industry and academic areas
Year(s) Of Engagement Activity 2020
 
Description YC: 13th International Conference on Nitride Semiconductors 2019 (ICNS-13), Bellevue, Washington, USA, 7th-12th July 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact The presentation reports design and then fabrication of Monolithic On-Chip Integration of HEMTs/Green LEDs. The results provided a new direction to move forward developing a new prototype optoelectronics. It is expected to draw strong attention from industry.
Year(s) Of Engagement Activity 2019
 
Description YC: 2019 UKNC Conference, Glasgow, UK, 9-10th January 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact present latest results on developing Monolithic integration of GaN HEMTs and green LEDs for Li-Fi application
Year(s) Of Engagement Activity 2019