CitationDownload as .RIS
Emerald Group Publishing Limited
Copyright © 2011, Emerald Group Publishing Limited
Green Photonics Conference, Millennium Centre, Cardiff, 19 October 2010
Article Type: Exhibitions and conferences From: Soldering & Surface Mount Technology, Volume 23, Issue 2
During October, the Centre for Advanced Functional Materials and Devices (CAFMaD) held its one-day conference on green photonics at the impressive new Millennium Centre in Cardiff Bay. The meeting was opened by Gary Reed of CAFMaD and the morning session was chaired by Professor Andrew Evans from Aberystwyth University. The first presentation was given by Dave Rimmer of DREM Ventures Ltd and it was on the subject of the Welsh Optoelectronics Forum (WOF) and its enabling activities in green photonics. The WOF was established in 1996 by the Welsh Development Agency and it now has over 100 member companies. WOF is an industry-facing organisation that works closely with academia and government and offers valuable networking opportunities across the full breadth of optoelectronics technology capability from materials, through components and systems, to equipment. Photonics has the potential to help save energy and cut greenhouse gas emissions via the use of new materials, energy reduction techniques, more efficient networks, improved product design and performance and via sustainable manufacturing and reduced pollution. Dave concluded by detailing some of WOF’s achievements to date, which included the development of various roadmaps.
Andrew Evans then presented “fast throughput characterisation of multilayer devices by real time spectroscopy”. He began by giving an overview of the activities of CAFMaD, which was a partnership between Aberystwyth and Bangor Universities, in areas such as organic electronics, extreme materials, sensors and devices and characterisation. Andrew then moved on to discuss solar energy collection and the optimisation of light conversion and the potential for the various configurations of organic photovoltaic devices, based on small organic molecules, polymers and hybrid organic-inorganic materials. Computational and visualisation studies were useful for predicting the interfacial properties of these devices, but there was still some way to go in the further development of such approaches.
Dr Andrew Johnson of IQE plc then gave a talk on “utility scale power generation using third generation photovoltaics based on III-V semiconductor technology”. Silicon-based photovoltaics had efficiencies of around 20 per cent and a cost of around $2.5/Wp, whereas GaAs concentrator voltaics had the potential to achieve 40 per cent efficiency and a less than $1.0/Wp cost if used in combination with appropriate concentrator structures. By using multiple junctions, more energy could be harvested. The devices themselves were based on classic triple junctions grown epitaxially onto a germanium substrate. Multi-junction devices had by far the highest efficiencies and a recent report had indicated that an efficiency of 42 per cent had been achieved. The possibility of using a gallium arsenide substrate followed by subsequent III-V deposition using MOCVD had recently been investigated by IQE. A key challenge with these types of multi-junction cells was the lack of lattice matching between these materials at certain of the layer interfaces. Andrew concluded by stating that concentrated photovoltaic systems offered the highest efficiency solar conversion and the lowest cost per kilowatt hour. They were the best solution for use in hot climates, but would not be suitable for areas such as Northern Europe.
Professor Martin Taylor from Bangor University then spoke about the use of nano-structuring to improve organic photovoltaic cells. Organic PV efficiencies were being improved and, currently, the best efficiencies were currently in the region of 8 per cent. He began by demonstrating the equivalent circuit of a photovoltaic device and describing how organic PVs functioned. A problem with organic PVs is the limited diffusion length for excitons and this is why, nano-structuring is so important. Initial work had focussed on the nano-structuring of titania and other materials using a variety of techniques. The strategies and approaches used to increase the efficiency of these devices by various groups around the world were then reviewed. Martin concluded by describing how plasmonic field enhancement approaches using silver and gold nanoparticles were being used to modify the absorption spectrum and to give increased absorption.
The final talk of the initial session was about “photonics in Wales” and this was given by Professor John Harries on behalf of the Welsh Assembly Government. He reiterated that the future lay in a knowledge-based economy that relied on scientific, technological and engineering know-how. A Science Advisory Council for Wales was currently being established and an updated Science Policy Document first produced in 2006 was to be updated. John stated that there was a need to provide a clear case for photonics taking a leading position in the Welsh science and technology policy/base on which greater prosperity and expertise could be built.
The first presentation of the second morning session was given by Dr Rudi Winter from Aberystwyth University and he covered “dynamic studies of film nano-structures by grazing incidence of X-ray scattering”. The work had been carried out on ytrria-stabilised zirconia made via sols. The technique enabled the study of changes in nanostructural features such as porosity, grain size and orientation and was potentially useful for carrying out dynamic studies of the film structures of photovoltaic systems both during production and in use environments. As the technique was sensitive at the nanometre scale, changes could be detected in PVs long before macroscopic failure became evident.
Kevin Bygate of Tata Steel then discussed “turning buildings into power stations”. The concept was to use a building’s envelope to save, produce and export energy, while addressing worldwide sustainability issues, using appropriate building coatings. One example cited was the “transpired solar collector” which was a perforated metallic cladding with a conversion efficiency of around 50 per cent; 1,000 m2 of wall could equipped with such a collector could produce 0.5 MW. Tata were also working on the pilot production of dye-sensitised photovoltaic devices.
Professor David Walker of Glyndwr University then presented “optics for energy generation by laser fusion”. David began by stating that nearly all alternative energy sources were ultimately derived from solar energy and he highlighted that most of these sources did not produce a regular flow of energy. He then discussed the basics of nuclear fusion and fission. The USA’s national ignition facility was currently preparing to use laser beams to bring about nuclear fusion, while in Europe, the HiPER project was using a related approach to produce fusion which would then generate power via a steam turbine.
The keynote and final presentation of the morning session was given by Mike Lebby of Translucent Inc., and this was entitled “photonics becomes greener over the next decade”. He stated that photonics had a big part to play in renewables, but there were also several key barriers to be overcome. In 2009, Asia had owned 81 per cent of the global optoelectronics and photonics market. The green photonics market would grow from $3,538 million in 2009 to $5,169 million in 2021. He went on to detail the forecast trends in global system capacity and network traffic out to 2030 – there was unlikely to be a gap between capacity and traffic, as it would be controlled by costs and charges form the providers. An important role for green photonics would be in reducing power consumption and this would increasingly be achieved by nano-photonic integration. The consumer would increasingly drive the growth of green photonics; displays were going green and becoming more energy efficient. Projection photonics using new diode lasers would be a growth opportunity for projecting images, although power consumption was still an issue. There had been significant progress in the development of blue-green materials for laser diodes. Solid-state lighting was another major growth area and was predicted to represent 43 per cent of the lighting market by 2021. Optical sensors also had a key role to play in many green applications. Translucent were working on the use of rare earth oxides to lattice match different materials; by changing the metal, it was possible to control the characteristics of the device interfaces. Mike concluded by reiterating that photonics was green and would enable new technologies and products that would also be green.
Owen Guy from Swansea University began the afternoon session with a presentation on “green silicon” and this was about taking reclaimed wafers and converting them into PVs. The reclaimed silicon was obtained from companies such as Intel, who provided it initially for their own reuse. However, after several reprocessing cycles, at some point it became too thin and it was then used to make PVs. Using reclaimed wafers avoided the need to melt the silicon and thus there was less energy used in manufacture. The devices produced had 14-20 per cent efficiencies and long service lives. The properties and performance of these monocrystalline devices were then compared to other types of PVs. New antireflection coatings and metal contacts were being investigated, as were techniques for surface texturing. Flexible 80 μm thick silicon PVs had also been produced and the intention was to take the thickness down to 50 μm. Owen finished his presentation by confirming the importance of silicon as a key material for producing PV devices.
Professor Igor Perepichka from Bangor University then talked about the design of functional organic materials for plastic electronics and photonics. Organic semiconductors were now beginning to have an impact on the commercial sector as they were finding use in light emitting diodes, organic solar cells, sensors and a number of other applications. Igor then described the building blocks of the conjugated polymers used in such applications and how these could be used to produce narrow band gap materials. One example shown was the group of soluble low band gap polythiophenes. If they were fluorine functionalised, they could be used in photovoltaic applications. A large range of fluorine/benzothiophene polymers had been synthesised and characterised and the hope was that it would be possible to produce white light emission from a single polymer LED. Controllable patterns of some of these materials were possible via inkjet printing.
Dr Vincent Barrioz from Glyndwr University/OpTIC Technium then discussed the status of “thin film PV research activities in Wales”. The current installed global PV generation capacity was 22.9 GWp and this would grow to 30.0 GWp by 2014. Of this total, there was 1.4 GWp of thin film PV capacity installed in 2009. The world’s largest PV solar farm covered ∼4.45 km2. A key challenge for PVs was to reduce the cost per watt via improved efficiencies and, in this context, thin film was better placed than silicon to achieve the required gains. They were direct band gap semiconductors and required thinner layers, which used less material. The thin film route also tended to have fewer process steps and was amenable to roll-to-roll production. Thin film devices also offered better energy yields. The Welsh Assembly Government was supporting thin film PV research and there were also knowledge transfer and technology transfer centres within Wales. Work was underway to establish the supply chain for thin film PVs. In the current work being carried out, the devices were produced using an MOCVD process to deposit co-doped cadmium telluride with arsenic and chlorine. This offered a relatively simple process that gave greater control over materials. The work was part of the “SPARC” project which included four universities and eight industrial partners.
The final two presentations of the day were given by Steve Burt of G24 Innovations and Anthony Hurden of Grounded Innovation Ltd Mark covered the role of, and opportunities for, photonics in the development of G24i’s dye-sensitised solar cells and Anthony discussed solar electricity and how the UK could best meet this opportunity.
Overall, this was an excellent conference which, via a large number of presentations, covered a wide range of subject matter from basic materials research to end-user applications and markets. The organisers are to be commended for organising such an interesting and useful event, especially as it was held in the excellent new Millennium Centre in Cardiff Bay.