At the CNST energy research aims to innovate and improve energy technology focussing on:
Solar Energy Research
Worldwide energy usage is estimated to have been 500 exajoules per year and is expected to increase between 20 and 40 % by 2030. Fossil energy sources currently dominate the worldwide energy production. The increasing demand in energy usage will create a shortage in energy sources in the next few decades.
Solar energy research in CNST focuses on understanding how novel new materials and structures can be used to generate renewable energy through photovoltaic and concentrated solar thermal approaches. By understanding the fundamental limitations in the performance of these next generation energy generators, we are contributing to reducing global carbon emission and creating new manufacturing opportunities for local companies.
Carbon Nanotubes in Solar Cells
Carbon nanotubes are a new form of carbon that were discovered in the 1990s. Carbon nanotubes have many unique features such as being 1000s of times more conductive than copper and stronger than steel. Some carbon nanotubes are excellent absorbers of the energy in sunlight and the development of ways to exploit this property to do useful work is an emerging field of research globally.
CNST researchers have shown that carbon nanotubes can be used in perovskite solar cells to yield high efficiency devices and help with the stability and hysterisis issues often observed in these systems. Theoretical studies done by CNST researchers have shown that a multijunction carbon nanotube based solar cell could harvest as much as 65% of all sunlight energy, compared to only 32% for silicon based solar cells.
One of the well known properties of carbon nanotubes is their excellent electrical conductivity, and despite the presence of the oxide layer on the silicon substrate the resultant nanostructures were found to be very good electrodes. As silicon is used as the major component in all electronic components integration of light harvesting architectures bound to silicon substrates into current devices would be straightforward step, once the carbon nanotubes had been modified to "capture" sunlight and convert this into electrical energy.
Researchers within the CNST have also developed the means for chemically modifying carbon nanotubes including the attachment of light absorbing elements, such as porphyrins, which generate electrical current upon exposure to sunlight, thus allowing the construction of a Nano-Solar Cell.
The very rough surface means a relatively high number of porphyrins can be immobilised, which would lead to higher efficiency in these Nano-Solar Cells. Potentially any silicon surface could be similarly modified to become a Nano-Solar Cell, including glass window surfaces. As these are "nano-coatings" there should not be a serious impact on the window's light transmission.
Organic Photo Voltaic Devices
Photovoltaic cells based on organic materials (OPVs) are a promising alternative to current Solar Cell (Photovoltaic or PV) technology as they are cheap to produce, have lower energy costs in production compared to silicon based devices, are flexible and thus can be mounted on practically any substrates and have the potential to be completely transparent. OPVs have the potential of much faster payback than solar cells that are based on silicon technology and offer Australia the opportunity to provide for our own energy needs through local manufacturing. However current generation OPVs are substantially less efficient than silicon based PVs and have a reduced long-term stability. For this reason, OPVs are not yet being commercially manufactured in large quantities. An OPVs performance relies heavily upon the intrinsic properties of the active layer materials (i.e. the polymers used), and also on the extrinsic properties of other materials employed in their manufacture, especially at the interfaces between the different layers comprising the OPVs.
Rarely do polymeric materials have atomistically "clean" interfaces, unlike the inorganic/silicon based systems. By their nature, these interfaces are difficult to understand and, ultimately, to control and manipulate. The materials of the different layers tend to interpenetrate which can either be beneficial or detrimental to device performance.
Printable Solar Cells
For the past 50 years, the traditional solar panels seen on rooftops have been made from silicon. These cells are very expensive to produce because of the very large amounts of energy required to purify the silicon and expensive fabrication facilities that are not likely in Australia. Next generation solar cells, based on recently invented plastics are lightweight, inexpensive and flexible and can be used in a range of applications from carrier bags to windows.
The CNST is paving the way for a lucrative new clean energy industry through developing novel environmentally friendly materials and methods for fabricating plastic solar cells. Special emphasis is on high performing materials which can be processed and deposited using aqueous solvents and alcohols. Work is underway to utilise these materials for developing prototype devices with roll-to-roll compatible techniques such as slot-die printing and lamination. Main areas of research within the CNST include:
• Thermomehanical properties of materials for morphology optimization
• Development of low-cost and scalable fabrication methods such as printing
• Interface materials and engineering
• Surface physics of nanomaterials for device applications
This research is a promising alternative to the expensive fabrication techniques currently used in the renewable energy sector, and would make the commercialisation of plastic solar cell technology more viable.