Written by James Cave
One of the major goals of CDT-PV is to build collaborations, both between the seven universities taking part and with other organisations interested in developing solar technologies. Last May, I spent five weeks in Newcastle, Australia working on organic solar cells with Australia’s national research organisation, CSIRO.
A three hour train ride along the New South Wales coast north of Sydney, Newcastle is famous for having the largest coal export port in the world. This might not be the best start for a renewable energy project, but it also boasts the highly-rated University of Newcastle and CSIRO’s solar and energy research hub.
As a large, sunshine-abundant nation, Australia has much to gain by exploiting its solar resources. Aside from the obvious fact that the more sun you get on your panels the more electricity you’ll get out, solar power has huge potential in remote areas. Power transmission infrastructure is expensive, requiring construction of extensive networks of power lines, step-up and step-down transformers and then maintenance costs on top. For small, isolated settlements and installations, the cost per person of connecting to a conventional power station is massive. Solar modules can (and do!) help in this situation, generating power where you need it, without the need for a grid connection.
Currently, silicon technologies dominate the solar market due to their high efficiency and stability. Despite silicon solar panel prices plummeting over the last fifty years and continuing to fall today, solar is still expensive. Even with economies of scale from mass manufacturing and efficiencies pushing toward the theoretical upper-limit, silicon-based photovoltaics struggles to compete with other forms of power generation. This is in large part due to the cost of refining silicon to solar grade purity: an unavoidable expense.
This has led to much interest in alternative photovoltaic technologies, which is where CDT-PV comes in. For my placement in Newcastle, I was working on organic photovoltaics (OPV), a change from my PhD project on perovskites. Organic solar cells utilise small molecules, such as fullerene derivatives, and/or long polymers, especially ‘conjugated’ polymers with backbones of alternating single and double carbon-carbon bonds. These materials can be produced relatively cheaply, and their flexibility opens up the possibility of manufacturing the panels via efficient roll-to-roll (R2R) processing.
One of the main barriers for OPV deployment is low efficiencies. My project was to develop a computational model to study the effect of the morphology of a typical organic cell of the polymer P3HT and fullerene derivative PCBM* on its efficiency, adding a third material to the mix and replacing the P3HT* with another polymer PTNT*. We found that it is possible to squeeze more efficiency out of a three material system than you might otherwise expect by carefully choosing materials with the correct energy level structure and morphological properties.
If we can push down the price of solar electricity, and ideally combine it with cheaper energy storage, it will become possible to roll out (literally for organics) energy self-sufficiency for isolated areas with limited grid access.
I’m incredibly grateful for the opportunity to have visited Australia, to the SuperSolarHub for travel costs and to CSIRO for funding while there. It was a little daunting at first to be so far from home, but it was a great experience to work on a research project in a new location. For anyone else with the chance to work abroad, I would say definitely go for it.
*Polymer acronyms stand for:
P3HT – Poly(3-hexylthiophene-2,5-diyl)
PCBM – Phenyl-C61-butyric acid methyl ester
PTNT – poly(2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9- dihydrodithieno[3,2-c:3′,2′-h][1,5]naphthyridine-5,10-dione)
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Images by James Cave and used with permission.