Novel yellow phosphorescent iridium complexes with dibenzothiophene-S,S-dioxide-based cyclometalated ligand for white polymer light-emitting diodes

We have designed and synthesized two novel yellow phosphorescent iridium complexes using dibenzothiophene-S,S-dioxide-based cyclometalated ligand for the first time, which are capable of producing highly efficient yellow and white polymer light-emitting devices (PLEDs). The resulted iridium complexes display good thermal stability and high photoluminescence quantum yields. Both yellow and white PLEDs are fabricated with an identical single-emission-layer configuration of ITO/PEDOT:PSS/emission layer (EML)/CsF/Al. For the yellow phosphorescent PLEDs based on (p-CzFSOPy)₂IrPic, the best device performances with a peak luminous efficiency (LE) of 13.3 cd/A and a peak external quantum efficiency (EQE) of 5.3% are achieved. More importantly, the two-element WPLEDs containing iridium (III)bis (2-(4,6-difluorophenyl)-pyridinato-N,C^2′) picolinate (FIrpic) as blue and (p-CzFSOPy)₂IrPic as yellow phosphors doped into a PVK:OXD-7 matrix at an appropriate ratio exhibited a maximum LE of 19.2 cd/A, a maximum EQE of 9.6%, an extremely high luminance of 18717 cd/m² and Commission Internationale de L'Eclairage (CIE) coordinate of (0.317, 0.448). Moreover, at a luminance for practical application of 1000 cd/m², the LE still remains as high as 19.0 cd/A, with a very slight decrease.