Difference between photoluminescence and electroluminescence of excimer-based platinum [1, 3-difluoro-4,6-di(2-pyridinyl) benzene]chloride

A chromatically stable white phosphorescent organic light-emitting diode using platinum [1,3-difluoro-4,6-di(2-pyridinyl)benzene]chloride (Pt-4) dye as the emitting layer, producing both light blue-monomer and red-excimer emission, is obtained. We have investigated both photoluminescence (PL) and electroluminescence (EL) of Pt-4 dye, which appear to be very different. Whereas the PL spectra reveal monomer and excimer peaks at around 480 nm and 610 nm, the 480 nm monomer and 660 nm excimer emission are characteristic of the EL spectra. It is shown that in contrast to PL, which is ascribed to an energy transfer process, EL emission can be explained by direct hole trapping, which is deduced from the energy levels of Pt-4 dye and 1, 3-bis(9-carbazolyl) benzene host and demonstrated by current density–voltage characteristics of various concentrations.