Thermal Annealing Effects on the Absorption and Structural Properties of Regioregular Poly(3-Hexylthiophene) Films

Abstract

Regioregular poly(3-hexylthiophene) (P3HT) was synthesized by a Grignard metathesis method. The annealed and fast cooled P3HT films were studied by UV-vis absorption spectroscopy, atomic force microscopy, and grazing incidence X-ray diffraction (GIXRD) measurements. It is demonstrated that thermal annealing at around the onset temperature of the melting point of the polymer results in the annealed film having the highest interchain and intrachain orders while preserving the original morphological features. However, the film that has the highest or lowest crystallinity does not have the strongest or weakest absorption. The lack of clear correlation between the absorption spectra and GIXRD data is explained by a quasi-ordered phase model, in which crystalline, amorphous, and quasi-ordered chains interconvert into each other depending on annealing temperature.

Keywords:

• optical absorption
• phase conversion
• poly(3-hexylthiophene)
• thermal annealing

Acknowledgments

This work was supported by the National Natural Science Foundation of China (No. 20474066), the “100-talent Program” of Chinese Academy of Sciences, the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, and the President Foundation of Hefei Institute of Physical Sciences. The authors are grateful to Prof. Jinhuai Liu (Hefei Institute of Intelligent Machine, Chinese Academy of Sciences) for help in AFM experiments.