Amplified Spontaneous Emission Optimization in Regioregular Poly(3-hexylthiophene) (rrP3HT):poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) Thin Films through Control of the Morphology

The maximization of the optical gain of organic active materials is a crucial step in the development of organic lasers. In this paper we demonstrate that the amplified spontaneous emission (ASE) of regio regularpoly(3-hexylthiophene) (rrP3HT):poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) thin films is strongly affected by the film morphology, controlled by changing the solvent used for the spin-coating deposition. The solvent variation results in ASE threshold changes of up to 8-fold due to the variation in the uniformity of the two polymers mixing, determining the optical gain, and the morphology uniformity, affecting the losses. Our results demonstrate that the morphology optimization is a very important step in the development of organic materials with high optical gain.