Poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MeH-PPV) Amplified Spontaneous Emission Optimization in Poly(9,9-dioctylfluorene(PFO):MeH-PPV Active Blends

Abstract

In this paper we quantitatively investigate the effect of blending in an active polymer host on the Amplified Spontaneous Emission (ASE) properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MeH-PPV). In particular we investigate the ASE dependence of polymer:polymer blends of poly(9,9-dioctylfluorene) (PFO) and (MeH-PPV) on the blend composition. We show that ASE from the 0–1, 0-0 and even dual band is observed in the sample with a relative MeH-PPV content of 10% and that the lowest ASE threshold and the strongest ASE intensity increase with the excitation density are obtained for a MeH-PPV relative content of 25% in weight, with a threshold decrease of 26 times with respect to neat MeH-PPV films. These effects are ascribed to the interplay between the increase of Förster Resonant Energy Transfer from PFO to MeH-PPV dominating up to a MeH-PPV content of 25% and the increase of MeH-PPV aggregation, dominating at higher values of the MeH-PPV content. We also demonstrate that the blend content affects the local emission properties due to variations of the uniformity of the MeH-PPV distribution within the PFO matrix, of MeH-PPV clustering and aggregation. Beyond improving the understanding of the PFO:MeH-PPV interaction in active blends our results can be exploited for the optimization of organic optically pumped lasers based on active polymer:polymer blends.