Dual band amplified spontaneous emission in the blue in Poly(9,9-dioctylfluorene) thin films with phase separated glassy and β-phases

Abstract This paper reports the first experimental evidence of multiple band Amplified Spontaneous Emission (ASE) in the blue spectral range from a thin film of poly (9,9-dioctylfluorene) (PFO) with uniform thickness. In particular we demonstrate that ASE peaked at 453 nm and at 468 nm can be simultaneously obtained, with a threshold of about 255 μJcm−2 and 180 μJcm−2. This result is ascribed to the presence in the film of a uniform layer with PFO molecules fully in the glassy-phase spatially separated from micrometric clusters with molecules in the β-phase. The spatial separation between the two phases prevents energy transfer from the glassy to the β-phase, thus allowing both phases to show ASE. Beyond improving the understanding of the PFO based thin films with ASE our results open the way to the realization of broadly tunable optically pumped organic blue lasers.