Tuning crystalline ordering by annealing and additives to study its effect on exciton diffusion in a polyalkylthiophene copolymer

Mithun Chowdhury, Muhammad Tariq Sajjad, Victoria Savikhin, Noemie Hergue, Karina Sutija, Stefan Oosterhout, Michael F Toney, Philippe Dubois, Arvydas Ruseckas, Ifor David William Samuel

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23 Citations (Scopus)
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Abstract

The influence of various processing conditions on the singlet exciton diffusion is explored in films of a conjugated random copolymer poly-(3-hexylthiophene-co-3-dodecylthiophene) (P3HT-co-P3DDT) and correlated with the degree of crystallinity probed by grazing incidence X-ray scattering and with exciton bandwidth determined from absorption spectra. The exciton diffusion coefficient is deduced from exciton-exciton annihilation measurements and is found to increase by more than a factor of three when thin films are annealed using CS2 solvent vapour. A doubling of exciton diffusion coefficient is observed upon melt annealing at 200 °C and the corresponding films show about 50% enhancement in the degree of crystallinity. In contrast, films fabricated from polymer solutions containing a small amount of either solvent additive or nucleating agent show a decrease in exciton diffusion coefficient possibly due to formation of traps for excitons. Our results suggest that the enhancement of exciton diffusivity occurs because of increased crystallinity of alkyl-stacking and longer conjugation of aggregated chains which reduces the exciton bandwidth.
Original languageEnglish
Pages (from-to)12441-12451
JournalPhysical Chemistry Chemical Physics
Volume19
Early online date24 Apr 2017
DOIs
Publication statusPublished - 2017

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