Highly efficient solution-processed pure yellow OLEDs based on dinuclear Pt(ii) complexes

Pure yellow light is very important in monochromatic lighting and signal systems. However, there are very few efficient yellow phosphorescent complexes for solution-processed OLEDs. Here, we report two thermally stable dinuclear Pt(ii) complexes decorated with diphenylsulfone and arylboron groups. The two functional groups have little contribution to the lowest excited states but are significantly involved in the closely located higher lying excited states. The resultant complexes show pure yellow emissions with impressively high photoluminescence quantum efficiencies close to 0.9 in doped films. Besides, the solubility is improved due to the bulky substituents. Therefore, these dinuclear Pt(ii) complexes are employed to fabricate solution-processed OLEDs. All devices display pure yellow emission with Commission Internationale de L'Eclairage (CIE) coordinates around (0.44, 0.55). Furthermore, the 2 wt% doped devices achieve excellent performance with an external quantum efficiency of 21.54% and a current efficiency of 76.64 cd A-1, which are among the highest efficiencies reported for solution-processed yellow phosphorescent OLEDs.