The role of alkane dithiols in controlling polymer crystallization in small band gap polymer:Fullerene solar cells |
| |
Authors: | Tiziano Agostinelli Toby A. M. Ferenczi E. Pires Samuel Foster Andrea Maurano Christian Müller Amy Ballantyne Mark Hampton Samuele Lilliu Mariano Campoy‐Quiles Hamed Azimi Mauro Morana Donal D. C. Bradley James Durrant J. Emyr Macdonald Natalie Stingelin Jenny Nelson |
| |
Affiliation: | 1. Department of Physics, Blackett Laboratory, Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom;2. School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff CF24 3AA, United Kingdom;3. Department of Chemistry, Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom;4. Institut de Ciència de Materials de Barcelona, Bellaterra 08193, Catalunya, Spain;5. Konarka Austria, Altenbergerstrasse 69, Linz A‐4040, Austria;6. Christian Doppler Laboratory for Surface Optics, Johannes Kepler University, Linz, Austria;7. Department of Materials, Centre for Plastic Electronics, Imperial College London, London SW7 2AZ, United Kingdom |
| |
Abstract: | The effect of the addition of 1,8‐octanedithiol (ODT) during processing on the microstructure of blend films of poly[2,6‐(4,4‐bis‐(2‐ethylhexyl)‐4H‐cyclopenta[2,1‐b;3,4‐b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)] (PCPDTBT) and [6,6]‐phenyl‐C71 butyric acid methyl ester ([70]PCBM) is studied. Grazing incidence X‐ray diffraction and absorption spectroscopy show that the crystalline order of PCPDTBT increases when ODT is introduced in the solution phase either to neat polymer systems or to blends with [70]PCBM. The increased crystalline order is accompanied by less dispersive hole transport in the polymer, and leads to a more efficient formation of a percolating fullerene network within the blend. This contributes to an increase in photocurrent generation. However, the bimolecular recombination rate as determined from photovoltage transients increases upon addition of ODT, limiting the power conversion efficiency to values well below those expected from the energy levels of PCPDTBT. We propose some explanations for this increase in bimolecular recombination, based also on variable angle spectroscopic ellipsometry measurements. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011 |
| |
Keywords: | additives blends charge transport conjugated polymers crystallization fullerenes |
|
|