Photoluminescence characteristics of blue phosphorescent Ir3+-compounds FIrpic and FIrN4 doped in mCP and SimCP

Absorption and photoluminescence (PL) characteristics are investigated in detail for blue phosphors iridium bis (4,6-difluorophenypyridinato-N, C2’) picolinate (FIrpic) and iridium bis (4,6-difluorophenylpyridinato-N, C2’)[5-(2-pyridyl)tetrazolate] (FIrN4) and for ultraviolet fluorescent materials 1,3-bis (9-carbazolyl) benzene (mCP) and 3,5-bis (9-carbazolyl) tetraphenylsilane (SimCP) at 10–300 K. The energies of the S1 and T1 states are estimated for FIrpic, FIrN4, mCP and SimCP from the absorption and excitation spectra. The PL intensities of FIrpic and FIrN4 doped in mCP and SimCP films are observed to decrease above about 50 and 150 K, respectively, with increasing temperature from 10 to 300 K. In all the neat films of mCP and SimCP, the 0–0, 0–1 and 0–2 vibronic bands of the T1 emission split into four and six components, respectively, indicating presence of aggregates such as dimer besides monomer. It is suggested that the aggregates lead to reduce the PL intensity of the dopants at high temperatures like room temperature.