A detailed study on the thermal transition of poly(3-hexylthiophene) (P3HT) and blends was investigated by differential scanning calorimetry, while the morphological, phase separation and the transformation in the optical properties were probed by thermal-atomic force microscopy (AFM), polarized optical microscopy (POM) and spectroscopic ellipsometry (SE). The inclusion of fullerenes on the polymer structure confirms the formation and evolution of a new endothermic transition at high temperatures. SE revealed that the refractive index and extinction coefficient of the films increased with annealing temperature up to 140 C due to the suppressed diffusion of PCBM molecules into the blend. Annealing above 140 C resulted in a decrease in the optical constants due to the formation of large ‘‘needle-like’’ crystals. This is due to the depletion of PCBM clusters near the ‘‘needle-like’’ structures; resulting from the diffusion of the PCBM molecules into the growing PCBM crystals or ‘‘needle-like’’ crystals as is evidenced by in situ thermal-AFM and POM. These findings indicate that annealing temperature of 140 C is suitable for a P3HT:PCBM film to obtain the desired phase separation for solar cell application.
Reference:
Malgas, GF, Motaung, DE and Arendse, CJ. 2012. Temperature-dependence on the optical properties and the phase separation of polymer–fullerene thin films. Journal of Materials Science, vol. 47(10), pp 4282-4289
Malgas, G., Motaung, D., & Arendse, C. (2012). Temperature-dependence on the optical properties and the phase separation of polymer–fullerene thin films. http://hdl.handle.net/10204/6558
Malgas, GF, DE Motaung, and CJ Arendse "Temperature-dependence on the optical properties and the phase separation of polymer–fullerene thin films." (2012) http://hdl.handle.net/10204/6558
Malgas G, Motaung D, Arendse C. Temperature-dependence on the optical properties and the phase separation of polymer–fullerene thin films. 2012; http://hdl.handle.net/10204/6558.
Copyright: 2012 Springer Verlag. This is the Pre/post print version of the work. The definitive version is published in Journal of Materials Science, vol. 47(10), pp 4282-4289.