Influence of Solvent Additive 1,8-Octanedithiol on P3HT:PCBM Solar Cells


A facile and efficient route is developed to improve the power conversion efficiency of poly(3-hexylthiophene-2,5-diyl):[6, 6]-phenyl-C61 butyric acid methyl ester (P3HT:PCBM) solar cells by processing solvent additive 1,8-octanedithiol (ODT) in the bulk heterojunction systems. The influence of ODT on polymer surface and inner
morphology, crystallinity, and quantitative molecular miscibility of P3HT and PCBM is studied. The results show that ODT enhances the phase separation of P3HT and PCBM and the P3HT crystallinity, increases the solubility of PCBM in P3HT, and reduces the size of amorphous P3HT domains. A high concentration of ODT induces the formation of a PCBM enrichment surface layer, which is beneficial for the device performance.

[1] Gholamkhass, B., Peckham, T. J., and Holdcroft, S. (2010). Poly(3-hexylthiophene)
bearing pendant fullerenes: Aggregation vs. self-organization. Polymer Chemistry,
vol. 1, pp. 708–719.
[2] Chen, H. Y., Yang, H., Yang, G., et al. (2009). Fast-grown interpenetrating network
in poly(3-hexylthiophene): Methanofullerenes solar cells processed with additive.
Journal of Physical Chemistry C, vol. 113, pp. 7946–7953.
[3] Razzell-Hollis, J., Tsoi, W. C., and Kim, J. S. (2013). Directly probing the molecular
order of conjugated polymer in OPV blends induced by different film thicknesses,
substrates and additives. Journal of Materials Chemistry C, vol. 1, pp. 6235–6243.
[4] Cho, S., Nho, S. H., Eo, M., et al. (2014). Effects of processing additive on bipolarfieldeffect transistors based on blends of poly(3-hexylthiophene) and fullerene bearing
long alkyl tails. Organic Electronics, vol. 15, pp. 1002–1011.
[5] Schaffer, C. J., Schlipf, J., Indari, E. D., et al. (2015). Effect of blend composition
and additives on the morphology of PCPDTBT:PC71BM thin films for organic
photovoltaics. ACS Applied Materials & Interfaces, vol. 7, pp. 21347–21355.
[6] Müller-Buschbaum, P., Kaune, G., Haese-Seiller, M., et al. (2014). Morphology
determination of defect-rich diblock copolymer films with time-of-flight grazingincidence small-angle neutron scattering. Journal of Applied Crystallography, vol. 47,
pp. 1228–1237.
[7] Kampmann, R., Haese-Seiller, M., Kudryashov, V., et al. (2004). The potential of the
horizontal reflectometer REFSANS/FRM-II for measuring low reflectivity and diffuse
surface scattering. Physica B, vol. 350, pp. E763–E766.
[8] Kampmann, R., Haese-Seiller, M., Kudryashov, V., et al. (2006). Horizontal ToFneutron reflectometer REFSANS at FRM-II Munich/Germany: First tests and status.
Physica B, vol. 385–386, pp. 1161–1163.
[9] Yao, Y., Hou, J., Xu, Z., et al. (2008). Effects of solvent mixtures on the nanoscale
phase separation in polymer solar cells. Advanced Functional Materials, vol. 18, pp.
[10] Li, G., Shrotriya, V., Huang, J., et al. (2005). High-efficiency solution processable
polymer photovoltaic cells by self-organization of polymer blends. Nature Materials,
vol. 4, pp. 864–868.
[11] González, D. M., Körstgens, V., Yao, Y., et al. (2016). Improved power conversion
efficiency of p3Ht: PCBM organic solar cells by strong spin-orbit coupling-induced
delayed fluorescence. Advanced Energy Materials, vol. 5, p. 1401770.
[12] Ruderer, M. A. (2012). Morphology of polymer-based films for organic photovoltaics.
PhD thesis, Technische Universitat Munchen, Munich, Germany.