“…Similar behavior of PL was previously noticed in our study of morphological stabilization of amorphous films by UV light of N,N ′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD), another well-known OLED material [21], and by other authors before us [22,23]. DPVBi and TPD have similar characteristics like molecular structure, UV-vis absorbance [24,25] and glass transition temperatures [26,27], but changes under UV light and oxygen are faster in DPVBi, what makes it easier to study.…”