1. Clarendon Laboratory; Department of Physics; University of Oxford; Parks Road Oxford OX1 3PU UK
2. Centre for Energy Studies; Indian Institute of Technology; Delhi 110016 India
3. Australian Center for Advanced Photovoltaics; School of Photovoltaic and Renewable Energy Engineering; Tyree Energy Technologies Building; University of New South Wales; Sydney 2052 Australia
4. Biomolecular and Organic Electronics; Department of Physics; Chemistry and Biology (IFM); Linköping University; Linköping SE-581 83 Sweden