Organic Chemists Contributing to the Development of Photovoltaics
Background - Why is this important?
The sun delivers more energy to the earth in one hour than we currently use from fossil fuels, nuclear power and all renewable energy sources combined in a year. Its potential as a renewable energy source, therefore, is vast.1
As a result, the conversion of inexhaustible solar energy into electrical energy using PhotoVoltaic (PV) devices is one of the most attractive solutions to clean, renewable energy and will transform our future energy options. Photovoltaic power generation is currently dominated by photovoltaic cells that are based on inorganic materials such as polycrystalline silicon, cadmium telluride and copper indium selenide. To make power from photovoltaics truly competitive with fossil-fuel technologies the cost needs to be reduced by a factor of 2-5.2 New Photovoltaic technologies, such as organic and dye-sensitised solar cells, are emerging from active research and development in the UK and elsewhere.
What did the organic chemists do?
Organic Photovoltaics (OPVs) are a promising cost-effective alternative to inorganic-based PV; and possess low cost, light-weight, and flexibility advantages. Organic molecules such as the polymer3 illustrated in the reaction scheme below have high optical absorption coefficients compared to their inorganic counterparts, and incorporation of polymers of this type into photovoltaic cells offers an attractive alternative to current technology.4
Palladium-catalysed coupling procedure to generate a diketopyrrolopyrrole polymer (Ref 3)
Creation of complex organic polymers relies on innovative synthetic organic chemistry. In the case illustrated above, the polymer was synthesised from its monomer using a palladium-catalysed coupling procedure. This method of carbon-carbon bond-formation was recognised for its contribution to the construction of complex organic molecules by the 2010 Nobel Prize for chemistry awarded to Professors Heck, Negishi and Suzuki.
Cells based on OPVs are currently relatively inefficient due to energy leakage problems and it is estimated that improvements in cell performance, operational stability and fabrication methods are needed to take power conversion efficiencies from the current levels of around 6-8% to a competitive 15%.5 Organic chemistry provides an opportunity to address this challenge at the molecular level, but it is recognised that the vast parameter space available will necessitate the definition and use of inspired molecular design guidelines.6 Success will provide significantly lower cost/higher volume manufacturing procedures of flexible devices that in turn will provide opportunities for the production of a wide range of new applications.
What is the impact?
There is already significant research related to enhancing the efficiency of solar conversion. Solar energy through photovoltaics will be a part of the energy mix of the future. This will require an interdisciplinary approach to generate novel photovoltaic materials and new advanced device concepts that will lead to commercialisation of high-efficiency and low-cost solar cells.
1 Solar Fuels and Artificial Photosynthesis, Science and innovation to change our future energy options, RSC, January 2012
2 H A Atwater, A Polman, Nature Mater., 2010, 9, 205
3 J R Durrant, I McCulloch et al, J. Am. Chem. Soc., 2011, 133, 3272
4 F He, W Wang, W Chen, T Xu, S B Darling, J Strzalka, Y Liu, L Yu, J. Am. Chem. Soc., 2011, 133, 3284
5 Y Yuan, T J Reece, P Sharma, S Poddar, S Ducharme, A Gruverman, Y Yang, J Huang, Nature Mater., 2011, 10, 296
6 J E Anthony, A Facchetti, M Heaney, S R Marder, X Zhan Adv. Mater., 2010, 22, 3876
Also of interest
Solar Fuels and Artificial Photosynthesis: Science and innovation to change our future energy options
18 January 2012
18 January 2012 - The RSC releases the UK’s first report on solar fuels and their potential environmental and economic benefits to the UK
Professor Akira Suzuki, Hokkaido University, Japan and Professor Ei-ichi Negishi, Purdue University, US were both recognised for their contribution to synthetic chemistry
24 February 2012
A UK researcher aims to level the playing field for solar cell efficiency claims with a set of simple guidelines
22 June 2010
Nanofibre electronic films based on multi-part organic molecules could boost organic solar cells
19 October 2009
Using small molecules to evenly space nanoparticles in a polymer composite could bring nanoparticle properties to a larger scale
Contact and Further Information
Dr Anne Horan
Programme Manager, Life Sciences
Royal Society of Chemistry, Thomas Graham House, Science Park, Milton Road, Cambridge, CB4 0WF
Tel: 01223 432699