White light emission from single layer poly (n-vinylcarbazole) polymeric light-emitting devices by mixing singlet and triplet excimer emissions

White light electroluminescence (EL) was obtained by mixing emission from singlet and triplet excimers from a single poly (n-vinylcarbazole) (PVK) spin cast layer after irradiation of the solution with UV light. With increased UV light irradiation, the intensity from the triplet excimer (red-630 nm) of PVK increased compared with that of the singlet excimer (blue-460 nm) due to an increased population of both adjacent benzene rings being aligned with one another (fully overlapping) versus only one of the adjacent benzene rings being aligned (partially overlapping). The emission color changed from blue to white with increased UV irradiation time while the EL brightness and current density decreased and the turn-on voltage increased.