becomes more pronounced at higher doping concentration in the film, which we assign to emission from an aggregate. To examine the nature of this aggregate, we measured the absorption spectrum of the neat film (Figure ) and found it to be identical to that in toluene solution. Thus, there is either too low a concentration of the aggregate in the film to be discernible by absorption spectroscopy or the low energy PL band results from excimer/exciplex-like emission, which are known for their poor absorption cross sections. For 5TABN2, and especially 6TABN3, this low energy feature in the PL spectrum is strongly supressed (Figures and). The FPL values at 3, 10 and 30 wt% doping are summarized in Figure .