Poly(4-vinyltriphenylamine): Optical, electrochemical properties and its new application as a host material of green phosphorescent Ir(ppy)3 dopant

Vinyl polymer PTPA containing pendant triphenylamine chromophore, which possesses hole-transport characteristics, was used as a host material in green phosphorescent light-emitting diodes. The PL spectrum of PTPA showed an intrinsic peak (375 nm) attributed to triphenylamine groups and an excimer emission (440 nm). The PL and EL spectra of the blends [PTPA:Ir(ppy)3] showed dominant green emission attributed to Ir(ppy)3 due to efficient energy transfer from PTPA to Ir(ppy)3. The HOMO level of PTPA, estimated from cyclic voltammetric data, was −5.36 eV, which is higher than −5.8 eV of PVK owing to hole-affinity characteristics of the pendant triphenylamine groups. The best performance was obtained with the EL device (ITO/PEDOT:PSS/PTPA:Ir(ppy)3 (1 wt%):PBD (40 wt%)/Ca/Al), the maximal luminance and the maximal luminance efficiency were 8358 cd/m2 and 4.5 cd/A, respectively. The present study suggests that the polymer PTPA is versatile host materials for green phosphorescent polymer light-emitting diodes applications.