Nanoscale Characterisation and Radiation Damage Testing of Organic Solar Cells

AAA solar simulator in operation at UCL.

AAA solar simulator in operation at UCL. Inset: OPV cell schematic & typical current-voltage curves in the dark and under illumination.
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Project Summary: Low-energy-gap conjugated polymers are attracting increased attention, as novel materials both for the fabrication of low-cost emitters in the Near Infra-Red (NIR) range of the optical spectrum, and for applications in plastic solar cells (or organic photovoltaics, PV). The latter are a low-cost, light-weight, flexible alternative to the historical inorganic cells. A low electronic gap will enable the exploitation of a spectral range that does not contribute to device efficiency in technologies based on higher gap materials. Although solar cells incorporating low-gap semiconductors suffer from a correspondingly lower open-circuit voltage (Voc), these devices can be used in tandem cells that incorporate higher-energy-gap materials such that the overall Voc becomes the cumulative sum of the individual components. In this manner, it is possible to boost device efficiency without detriment to the overall performance and range of applicability of the solar cell.

The project will focus on four key areas with a view to optimise device efficiency and long-term stability: (1) characterization of PV properties of solar cells incorporating low-gap materials using state-of-the-art facilities at UCL; (2) nanoscale structural and dynamical characterization using a wide range of Neutron Scattering techniques (diffraction, reflectometry, quasi-elastic neutron scattering[1]) at ISIS (UK), and other facilities worldwide; (3) investigation of the fundamental processes limiting cell efficiency, in particular, exciton splitting processes and related recombination of geminate polaron pairs via Scanning Near-field Optical Microscopy and Lithography-assisted photoconductivity [1-3]; and (4) effect of radiation exposure on all aforementioned parameters, on in essence cell performance, with the unique instrumentation available at ISIS. The PV cells will make use of blends of high-mobility, low-gap polymers blended with C60 and C70 derivatives.

This PhD program builds on unique research strengths at UCL and ISIS and seeks an enthusiastic student to join our multidisciplinary and multinational team in cutting edge research. You will be exposed to a very wide range of characterization techniques in organic photovoltaics, will work in a multidisciplinary/ multinational environment, and benefit from an extremely rich training programme that will include both “indoor (i.e. at UCL)” and “outdoor (conferences, summer schools, progress meetings and workshops)” training activities.

References

[1] García Sakai et al, Curr.Opin.Coll.Int. Sci.14, 381 (2009).

[2] Riehn et al, Appl. Phys. Lett. 82, 526 (2003).

[2] Fenwick et al, Nature Nanot. 4, 664 (2009)

[3] Riehn et al, Adv. Funct. Mat. 16, 469 (2006)

 

ISIS Supervisor: Victoria García Sakai, ISIS Facility, Rutherford Appleton Laboratory. Phone: 01235 446703, e-mail:victoria.garcia-sakai@stfc.ac.uk

UCL Supervisor:  Franco Cacialli, London Centre for Nanotechnology & UCL Dept of Physics & Astronomy.Phone: 020 7679 0647 (Ext: 34467), e-mail:f.cacialli@ucl.ac.uk

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