Polymer Centre Highlight: A Greener Route to Green Energy

Polymer centre academics; Dr Alan Dunbar, Dr Ahmed Iraqi, Dr Alastair Buckley and Prof David Lidzey have reported the manufacture of organic photovoltaic devices from non-halogenated binary solvent blends. This work was carried out in collaboration with Dr Andrew Pearson from the Optoelectronics Group at Cambridge University.

Organic photovoltaic devices (OPVs) have seen recent improvements in the power conversion, now being able to achieve 9 % efficiency. The performance achievable is approaching the benchmark which would allow OPVs to become commercially viable. OPVs use a conjugated polymer and fullerene derivative to act as a semi-conducting layer. However, currently OPVs require the use of halogenated solvents to dissolve and then deposit this essential semi-conducting layer. In order to produce environmentally acceptable OPVs, a suitable non-halogenated solvent must be found for the semi-conducting layer though the majority do not readily dissolve in such solvents.

Hansen solubility parameters were used to predict solvent systems that would dissolve the organic semi-conductor. This was achieved by using a system with similar solubilising properties to that of the halogenated solvent. The solvent system used was carbon disulphide (CS2) and acetone. Both are used commercially and have a lower toxicity than the halogenated solvents previously used. The solvent blend had a solubility limit of 20 mg ml-1 compared to 10 mg ml-1 of the halogenated solvent. This increase is attributed to blending allowing for a closer match to the solubility parameters of the organic semi-conductor.

OPVs produced using the solvent blend achieved power conversion values higher than those obtained from using a halogenated solvent, for both conjugated polymers used.

Original publication: Organic photovoltaic devices with enhanced efficiency processed from non-halogenated binary solvent blends, Griffin, J.; Pearson, A. J.; Scarratt, N. W.; Wang, T.; Dunbar, A. D. F.; Yi, H.; Iraqi, A.; Buckley, A. R.; Lidzey, D. G., Org. Electron. 2015, 21, 216-222.

Article by Luke Fox; a PhD Student on the EPSRC Polymers, Soft Matter and Colloids CDT programme. For more information, please contact Dr Joe Gaunt at the Polymer Centre.