Optical properties of poly(3-hexylthiophene) (P3HT) isolated chains and aggregates in solution: The role of chloroform stabilizer

With the improvement in synthetic methodologies, polythiophenes - specifically poly(3-hexylthiophene) (P3HT) - have become forerunners in the field of conjugated polymers. We study P3HT’s morphological and optical properties via measurements of absorption, photoluminescence (PL), and polarization-resolved Stokes spectropolarimetry. Our recent results show that P3HT’s aggregation behavior, in the precursor solution, changes drastically between using amylene-stabilized (Am-CHCl3) and non-stabilized chloroform (CHCl3). Particularly, P3HT solutions made from Am-CHCl3 presented H-aggregates, which is indicated by the higher PL intensity of 0-1 transition peak compared to 0-0 one. On the contrary, the similar samples diluted in CHCl3 exhibited J-aggregates with vibronic ratio  > 1. Our results indicate that the presence of amylene promotes the formation of -stacks between neighbor polymer chromophores and shortens conjugation length, leading to the formation of H-aggregates. To rule the influence of amylene out, we are currently performing a set of analyses and experiments consisting of various P3HT chain sizes and blended MeOH@CHCl3 solvents.