Enhancement of Third-Order Optical Susceptibility in Polythiophene Thin Films Fabricated by Drop Casting Using Anhydrous Solvent

Third-order optical susceptibility of ordered and disordered polyfluorene thin films

“…The obtained enhancement of χ (3) is smaller and the χ (3) values themselves are lower than those reported for P3HT [6,7]. To compare the χ (3) values of various conjugated polymers, in Fig.…”

“…4 demonstrates that the enhancement in β-phase F8 is not larger than that of the − 6 power law. As Kishida et al reported [6], the enhancement beyond the law is certainly observed in our data for P3HT [7] although the higher value is not very far from the dashed line representing the law in Fig. 4.…”

“…The maximum χ (3) values of the one-dimensional conjugated polymers are probably always limited by the −6 power law; however in some cases, the polymers may show lower values than those expected from their E g . For example, conjugated polymers with a relatively low ionization potential (IP), such as P3HT, may be affected by oxygen and water in air at ambient conditions, resulting in a significant decrease in their χ (3) value, while their optical gap is unchanged [7]. For this reason, we prepared P3HT thin films in an inert atmosphere.…”

“…The F8T2 thin films were drop cast from a toluene solution; the ordered and disordered P3HT thin films were spin coated and drop cast, respectively, from chloroform solutions. Because P3HT is unstable in the presence of oxygen and water, we used an anhydrous solvent and measured the EA spectra of P3HT without exposing it to ambient air [7]. The concentrations of the prepared solutions were tuned to produce 100-nm-thick films for all the polymers.…”

“…Therefore, a conjugated polymer with large E g but long effective conjugation length may exhibit high χ (3) values. For some conjugated polymers with relatively small E g , χ (3) can be enhanced by improving the crystallinity of thin films [5][6][7]. It was also reported that, in some cases, the enhancement is beyond the limitation of the − 6 power law [6].…”