Fluorescence and phosphorescence behavior of TPD doped and TPD neat films

Photoluminescence spectra of N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD) are studied in a temperature range from 10 K to room temperature using a neat TPD film, and 5 wt.% TPD doped films with polystyrene (PS), 4,4′-N,N′-dicarbazole-biphenyl (CBP), and polycarbonate (PC) as hosts. The photo-excitation occurred in the singlet absorption region of TPD. The blue fluorescence and green phosphorescence quantum yields, ϕF and ϕP, of TPD are determined from their quantum distributions, EF(λ) and EP(λ). The yields are found to be ϕF = 0.39 and ϕP = 0.012 for neat films at room temperature, while ϕF = 0.78 and ϕP = 0.026 are measured for a TPD doped PS film. The lower luminescence quantum yield in the neat film is caused by self-quenching.