Low threshold Amplified Spontaneous Emission properties in deep blue of poly[(9,9-dioctylfluorene-2,7-dyil)-alt- p -phenylene] thin films

Amongst the different optoelectronic applications of conjugated polymers, the development of new active materials for optically pumped organic lasers is still an open question particularly in the blue-near UV spectral range. We investigate the emission properties of poly[(9,9-dioctylfluorene-2,7-dyil)- alt-p-phenylene] (PFP) neat films under nanosecond pump. We demonstrate that thanks to the introduction of a phenylene moiety between two fluorene units it is possible to obtain Amplified Spontaneous Emission (ASE) with a lower threshold and a blue shifted wavelength with respect to poly(9,9-dioctylfluorene) (PFO). We demonstrate efficient ASE with a minimum threshold as low as 23 μJcm−2 and a minimum ASE wavelength of 436 nm. A maximum net optical gain of about 26 cm−1 is measured at an excitation density of 0.23 mJcm−2. These results make the PFP a good active material for optically pumped deep blue organic lasers.