Manipulation of Pt···Pt Interaction in Platinum Complex by Methyl Group to Achieve Single-Doped White OLEDs: An Approach to Simulation of Daylight from Dawn until Dusk

White organic light-emitting diodes (WOLEDs) possess excellent electro-optic conversion efficiency for state-of-the-art light sources and play an important role in energy consumption and carbon emission reduction. Because of the multiple cells or multiple emitters, the structure of normal WOLEDs is sophisticated, resulting in high fabrication costs and low long-term stability. To overcome these hurdles, WOLEDs based on platinum (Pt) complexes with a single light-emitting layer demonstrate promising potential. Herein, we report the regulation of Pt···Pt interaction of Pt(II) complexes by methylation of the ligand tuning the emission of monomer and excimer, resulting in realizing correlated color temperature (CCT) adjustable WOLEDs. Single-doped WOLEDs based on Im2PhPtCl with CIE coordinates of (0.32, 0.36), color rendering index (CRI) over 83, high external quantum efficiency (EQE) of 24.4%, and low-efficiency roll-offs (EQE = 23.9% at 1000 cd m –2, EQE = 20.7% at 5000 cd m –2 ) are accomplished by using exciplex as a host. More importantly, the CCT of the WOLEDs could be tuned between 2751 and 7061 K by simply changing the driving voltages and closely matching with daylight locus from dawn until dusk. The outstanding device performances illuminate the state-of-the-art for WOLEDs, and their further applications may let people enjoy sunbathing indoors.