High-efficiency and low efficiency roll-off near-infrared fluorescent OLEDs through triplet fusion

• Published in: Chemical science (Cambridge) 2016-04, Vol.7 (4), p.2888-2895
• Main Authors: Xue, Jie, Li, Chen, Xin, Lijun, Duan, Lian, Qiao, Juan
• Format: Article
• Language: English
• Subjects: Blends; Chemistry; Displays; Emission; Fluorescence; Molecular orbitals; Organic light emitting diodes; Quantum efficiency
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c5sc04685h

Though urgently needed, high-performance near-infrared organic light-emitting diodes (NIR-OLEDs) are still rare. NIR-OLEDs based on conventional NIR fluorescent materials usually suffer from low external quantum efficiencies (EQEs) because of the intrinsic obstacles according to the spin-statistics limit and energy-gap law. Herein, we realized high-efficiency and low efficiency roll-off fluorescent NIR-OLEDs through efficient triplet fusion of a bipolar host doped with a special naphthoselenadiazole emitter (4,9-bis(4-(2,2-diphenylvinyl)phenyl)-naphtho[2,3- c ][1,2,5]selenadiazole, NSeD). Unlike typical NIR organic donor-acceptor (D-A) chromophores, NSeD features a non-D-A structure and a very large HOMO/LUMO overlap and displays a strong deep-red to NIR fluorescence and unique ambipolar character. The corresponding photoluminescence quantum efficiency of NSeD reaches 52% in solution and retains 17% in the blend film. The optimized NIR-OLEDs demonstrated a strong emission at 700 nm, a high maximum EQE of 2.1% ( vs. the predicted theoretical maximum efficiency of 1.3%) and the EQE remained at around 2% over a wide range of current densities from 18 to 200 mA cm −2 , which is amongst the highest performance for NIR-OLEDs based on organic fluorescent materials. High-efficiency and low efficiency roll-off near-infrared fluorescent OLEDs are realized through effective triplet fusion of a bipolar host doped with a special non-donor-accepter naphthoselenadiazole emitter.