Efficient multi-light-emitting layers warm and pure white phosphorescent organic light-emitting diodes with excellent color stability.

The warm white organic light-emitting diodes (WOLEDs) consisting of four emissive layers (EMLs) as well as pure WOLEDs consisting of three EMLs have been fabricated by using three primary color phosphors as emitters. Experimental results demonstrated that energy transfer between dopants, direct carriers' trapping and main recombination zone are all important factors in determining the performances of obtained devices. By precisely managing dopants' concentrations and emitting layers' thicknesses, we realized the optimized warm WOLED with a Commission Internationale de l'Eclairage coordinates (CIE x,y) of (0.388, 0.383), giving the highest current efficiency (η c) of 69.00 cd/A, power efficiency (η p) of 60.19 lm/W and external quantum efficiency (EQE) of 20.63%. Additionally, by increasing the proportion of blue emission, we also realized the pure WOLED (CIE x,y value is (0.331, 0.385)) giving 60.48 cd/A (EQE = 16.90%, CRI = 72.03) and 51.32 lm/W in highest η c and η p , respectively. Especially, the optimal warm and pure WOLEDs exhibited the superior color stability with small CIE discrepancies of (0.020, 0.003) and (0.022, 0.004) in the range of 1–10 mA/cm2, respectively. Efficient multi-light-emitting layers warm and pure white phosphorescent organic light-emitting diodes (WOLEDs) with excellent color stability were fabricated by using PQ 2 Ir (dpm) (PQ = phenylquinoly-N,C20', dpm = dipivaloylmethane), Ir (mppy) 3 (tris(2-(4-tolyl)-phenylpyridine)iridium) and FIrpic (iridium (III)bis [(4,6-difluorophenyl)pyridinato-N,C20'picolinate) as red, green and blue emitters, respectively. Image 1 • Efficient warm and pure white phosphorescent organic light-emitting diodes were designed and fabricated. • Efficient energy transfer and direct carriers' trapping helps to realize high performance WOLEDs. • Well-matched energy levels help to balance carriers' distribution. • The designed devices displayed greatly improved injection and transport of electrons. [ABSTRACT FROM AUTHOR]