Here S is the Huang-Rhys factor and Eph is the phonons energy. A large value of S is related to significant degree of carrierphonon coupling, indicative of either emission by STEs or phonon mediated detrapping and radiative recombination. Indeed, for the two samples with broadband emission, 1,3-PDA and 1,4-PDA, we obtain respectively S=39.09 and S=131.6. For the excitonic component of 1,4-XDA on the other hand we obtain and S=8.58 with Eph=12.12 meV. Values of S >10 have been associated with the presence of STEs in perovskites and organic materials: in the broadband emitters, the coupling between phonons and carriers is compatible with the formation of self-trapped exciton which can explain the broad emission from these samples. In particular, the bright 1,4-PDA has the largest Huang-Rhys factor, indicating very efficient coupling with phonons with E = 13 meV. On the contrary, the value of S extrapolated for the last sample (1,4-XDA) is small, which agrees with an emission due to recombination of free excitons. Further indication on the nature of the broad emission comes from the pump fluence dependence of PL (Figure ). Fitting the intensity of emission in function of the incident power with a power law I=P K we estimate exponential K (Figure ): the values K1,3-PDA=0.745 and K1,4-PDA=0.835, lower than 1, indicate a recombination pathway mediated by defects leading to the formation of self-trapped excitons. A purely excitonic recombination on the other hand is expected to yield a power dependence with K = 1. However, it is no possible to compare this power law with the narrow emission of 1,4-XDA: its small Stokes shift results in significant reabsorption in powdered single crystal samples, distorting the measured spectrum.