“…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.…”