Consortium on organic solar cells meets for first time in Wollongong

Feb 08, 2007

Australia has identified the contribution of renewable energy resources as an important approach to the issue of climate control and is vastly well-endowed with a land mass that receives a large flux of solar energy.

Organic solar cell devices will be an important future solution to the provision of renewable energy resources in the world. A project involving the University of Wollongong (UOW) aims to deliver this as a sustainable energy source for Australia.

A group of Australian researchers with world-class ability to contribute in this area has formed an international consortium - this consortium met for the first time at UOW on February 5 and 6.

The consortium consists of Australian researchers from the University of Melbourne, University of Wollongong (Intelligent Polymer Research Institute), University of Sydney, University of Newcastle, University of Queensland and CSIRO combined with international expertise. The industrial group (Merck) will provide expertise in the possible industrial scale-up of material synthesis and prospects for commercialisation.

Director of the Intelligent Polymer Research Institute and the Australian Research Council Centre of Excellence in Electromaterials Science, Professor Gordon Wallace, said that the consortium would provide breakthrough results that would make Australia a world leader in the technology of large area low cost organic photovoltaic devices.

The successful outcome of this project will allow Australia to develop a new high value export industry, which will attract substantial foreign investment for R&D and the creation of substantial employment opportunities particularly for highly skilled workers, he said.

One of the participants in the consortium was Professor David Officer (formerly Massey University, New Zealand) who has just joined UOW as Professor of Organic Chemistry and Professorial Fellow in the ARC Centre of Excellence in Electromaterials Science.

In New Zealand Professor Officer was Director of the Nanomaterials Research Centre (NRC) and Professor in Chemistry in the Institute of Fundamental Sciences. He set up the Nanomaterials Research Centre in 2001 to develop 'intelligent materials' using the tools of nanotechnology, building new materials from the bottom (molecular level) up. In 2004, he was awarded the New Zealand Institute of Chemistry HortResearch Prize for Excellence in the Chemical Sciences. He is a Fellow of the New Zealand Institute of Chemistry.

Professore Officer said that the emulation of photosynthesis -- the efficient and sustainable use of solar energy using renewable materials represents one of the great scientific challenges of the 21st century.

"Although silicon-based solar cell technology, which converts sunlight to electricity (photovoltaics), effectively demonstrates that most human activity could be sustained using solar energy, only a small proportion of global energy production derives from the sun in this way principally as a result of the high production cost of the technology," he said.

Professor Officer said that a wide variety of other inorganic semiconductor materials have been investigated for solar cells, some of them proving to be more efficient than silicon at 'harvesting' sunlight.

"However, both cost and environmental concerns over their widespread use currently prohibit their commercial development. Despite great effort, emulation of photosynthetic light harvesting using other materials has proved highly challenging. The greatest advances have been made in the development of photoelectrochemical and polymeric (plastic) solar cells, both of which are the subject of international commercialisation initiatives," he said.

"The most successful photoelectrochemical (PEC) solar cell to date is the commonly known Grätzel cell, which uses ruthenium polypyridyl-based dyes adsorbed on nanocrystalline films of titanium dioxide, a cheap material widely used as a pigment in paint or paper and as an abrasive in toothpaste and other cosmetic products.

"The Grätzel cell has demonstrated light-to-electricity conversion efficiencies of up to 12%, efficiencies comparable to commercial silicon-based solar cells. Although these cells perform better than silicon cells in low light conditions, the cell construction is typically a rigid glass 'sandwich", limiting their application," he said.

In contrast, Professor Officer said that plastic photovoltaics presents the tantalising possibility of producing flexible solar cells, or coatings that function as sunlight harvesting paints on roofs or even as an integral part of fabrics to produce electricity from sunlight.

He said that this potential revolution in power generation was made possible by the Nobel prize-winning discovery of MacDiarmid, Shirakawa and Heeger in 1977, who showed that chemically doping certain conjugated polymers increased their electronic conductivity by several orders of magnitude.

Since then, electronically conducting polymers have found application in such diverse areas as sensors, batteries, light emitting diodes, and polymer actuators. However, arguably the most exciting potential application for these unique materials is in the area of solar energy.

"Before conducting polymers can be commercially exploited in photovoltaic devices their power conversion efficiency, currently around 5%, needs to be improved," Professor Officer said.