Ageing of printable polymer solar cells

Solar power is by far the most abundant renewable energy source. However, at present its use is limited by the high cost of solar cells, so that we continue to obtain most of our power from fossil fuels. Polymer (plastic) solar cells are an exciting research field that aims to address this problem, as polymer solar cells could be made by simple manufacturing processes such as roll to roll coating. The result would be much lower cost solar cells, with much lower energy of production. Most research to date has focussed on the efficiency of such solar cells, and good progress has been made, leading to efficiencies approximately two thirds of commercial amorphous silicon solar cells.In this proposal we address the most important remaining issue, namely understanding and enhancing the lifetime of polymer solar cells. To do this we will combine advanced photophysical, morphological and chemical analysis of solar cells before, during and after operation to gain new insight into the factors controlling degradation of such cells. This will provide a solid foundation for developing strategies for extending the solar cell lifetime in the later part of the project.The operation of polymer solar cells depends critically on the nanometre scale arrangement of the materials, so we will use sophisticated electron tomography techniques to study the nanoscale morphology and how it changes with device operation. This will be complemented by optical and electronic measurements performed in-situ on operating solar cells. A further innovation will be to make nanoscale perforation of an encapsulation layer and combine it with electron beam techniques to study local degradation with nanometre resolution. This challenging programme requires collaboration between world-leading research groups in St Andrews, Changchun, and Glasgow to access the range of expertise and facilities to make major progress, and will lead to a new UK-China collaboration.

Economic and Societal Impact The proposed research has significant potential for societal, commercial and academic impact. Renewable energy is a global issue and it is no overstatement to declare that our existence depends on a step-change in provision and attitude towards sustainable alternatives to fossil fuels. Significant changes in this direction will need to be met by a collection of technologies - e.g. solar (heating and photovoltaics), wind, tidal, nuclear, biomass/biofuels, ground and air source heating - to target the full range of consumers (i.e. commercial and private/domestic use). At present the use of solar photovoltaics is extremely limited because the cost is much higher than for electricity generated by burning fossil fuels, so the key challenge is to reduce the cost. The simple fabrication at low temperature of organic photovoltaic (OPV) devices, and in particular polymer solar cells, provides a promising route to achieving this and impressive progress towards demonstrations of roll to roll manufacturing is being made. This in turn brings into focus the need to develop an understanding of degradation mechanisms in such devices and identify the best materials and architectures for stable devices. Communications and Engagement After patenting any inventions arising from the project we are keen to present our results to companies as well as to other academics. We also foresee tremendous opportunities for public engagement. In addition to presenting results at major academic meetings such as MRS, we will also present at meetings with a more industrial bias (including those of the Photonics and Plastic Electronics KTN). We will of course disseminate our results through the scientific literature, targeting leading journals such as Advanced Materials. We are excited about the potential for public engagement that this project will bring, and plan to involve the appointed researchers (and ourselves) in public engagement activities. Collaboration and Exploitation A key strength of the project is the complementary skills of the teams in St Andrews, Changchun and Glasgow. As explained in the proposal, we will make the most of these capabilities via face to face meetings every six months, monthly videoconferences and exchange of researchers. All the investigators have considerable experience of filing patents, many of which have been granted and/or licensed. IDWS has recent experience of both licensing and spin-out routes to commercialise several organic semiconductor inventions. This experience will be invaluable for recognising and implementing the most appropriate exploitation route for results arising from the project. The exploitation route will take account of the status of the technology and associated IP, the potential markets and the possible routes to those markets. It is likely to involve collaboration with companies, and the most appropriate choice depends on the nature of the innovation. Candidates include the project partners Konarka and ECN (see letters of support), as well as Merck (Southampton), SolarPress (London) and Polysolar (Cambridge). Professional support is available from the Research and Enterprise departments of the Universities and via the Knowledge Exchange Office of the Scottish Universities Physics Alliance. We plan to put in place a collaboration agreement at the start of the project which defines partner responsibilities, distribution of finances and agreed mechanisms for knowledge exchange and the protection and exploitation of IP.