We next investigated the photophysical properties of the emitters when dispersed in the inert polymeric host, polymethylmethacrylate (PMMA), first at a doping concentration of 10 wt% emitter compared to the host. When recorded in air, the PL spectrum of each emitter was noticeably broader compared to that in toluene, which is unusual considering the suppression of molecular vibrations that is induced by the solid matrix compared to the free-flowing solution. The degree of broadening experienced by each emitter is not constant, with 6NICz and 5NICz having a FWHM that is 3.0× and 2.6× wider than in toluene, respectively, while the FWHM of 6,10NICz and 4NICz are approximately twice as wide (1.9× and 1.8×, respectively), and the FWHM of 7NICz remained relatively narrow, being only 1.5× wider than in toluene. This broadening is likely caused by contributions to the emission from aggregates, considering the relatively high doping concentration and the planar structure of the emitters. Because of this variable broadening, the λPL of the 10 wt% doped films in PMMA no longer follows the expected pattern of 6/6,10NICz > 4NICz > 5/7NICz, but in general the PL of all the emitters is slightly red-shifted. However, a similar pattern to the trend in lPL in toluene is observable in terms of the onset of the emission, except that 6NICz and 6,10NICz