Spectral variation of solution-processed blue bis[(4,6-difluorophenyl)-pyridinato-N,C2′] (picolinate) iridium(III) phosphor

Abstract

Spectral properties of a blue phosphorescent bis[(4,6-difluorophenyl)-pyridinato-N,C2′] (picolinate) iridium(III) (FIrpic) complex were systematically investigated. The electroluminescent spectra of FIrpic in solution-processed organic light-emitting diodes (OLEDs) were focused on, and the effects of doping ratio and solvent solution on spectral characterization were explored in solution-processed blue OLEDs. The results showed that there was an unusual spectral variation between shoulder and peak intensities in the electroluminescent spectra of FIrpic, and the intensity ratio of the shoulder to the peak (the Huang-Rhys factor) was obviously increased when FIrpic was at high doping ratios and dissolved in polar solvents. The theoretical mechanism for this phenomenon was analyzed, indicating that the spectral variation was due to solvation effect induced by strong intermolecular interaction between the solvent and FIrpic molecules. Moreover, the spectral behavior of FIrpic in solution-processed white OLEDs with complementary colors was studied, providing further evidence for the spectral variation.