Enhanced near-infrared electroluminescence from a neodymium complex in organic light-emitting diodes with a solution-processed exciplex host

Abstract

We report the enhanced near-infrared (NIR) electroluminescence from a Nd 3+ -complex with thenoyltrifluoroacetone and 1,10phenanthroline ligands. The NIR-emitting complex was blended into an exciplex-forming co-host system comprising 2,7bis(diphenylphosphoryl)-9,9'-spirobifluorene as the electron transport material and 4,4',4"-tris(carbazol-9-yl)triphenylamine as the hole transport material, in solution-processed small molecule organic light-emitting diodes (OLEDs). This binary ambipolar host system favors direct charge trapping and exciton formation on the Nd 3+ -complex molecules. Efficient energy transfer from the singlet and triplet exciplexes formed between the host molecules to the Nd 3+ ions contributes to the enhanced luminescence efficiency. The photoluminescence quantum yield of this blend is 1.2%, and the optimized OLED shows a maximum electroluminescence external quantum efficiency of 0.034%. The device also exhibits a low efficiency roll-off of only 12% over a current density range of 100 mA/cm 2 , due to the reduced triplet-polaron annihilation.

Review on the Electroluminescence Study of Lanthanide Complexes

“…The PLQY of Nd‐6 doped film was about 0.5%, and the optimized device ITO/PEDOT:PSS/mCP: Nd‐6 /TPBi/LiF/Al exhibited a maximum EQE of 0.022%. And in 2019, the authors changed the host materials of this device. With a structure of ITO/PEDOT:PSS/TCTA:SPPO13 (2,7‐bis(diphenylphosphoryl)‐9,9′‐spirobifluorene): Nd‐6 /TPBi/LiF/Al, the device reached a maximum EQE of 0.034%, which was more superior to the best value of solution‐processed NIR OLEDs and comparable to the best evaporation‐processed NIR OLEDs …”

Reducing the Efficiency Roll-Off in Organic Light-Emitting Diodes at High Currents under External Magnetic Fields

“…We have also previously shown that the exciton-polaron annihilation is primarily responsible for the roll-off in solution-processed lanthanide-based OLEDs. 42 In this study, however, our experiments evidence that the applied magnetic field can somehow supress the exciton-polaron annihilation. To better clarify this claim, we also present some example EQE values at different current densities without and with the magnetic field in Table . I.…”

Investigation progresses of rare earth complexes as emitters or sensitizers in organic light-emitting diodes

“…In 2019, Shahalizad et al fabricated Nd-1 (Fig. 9 ) based OLEDs by utilizing solution processing method 71 . Co-host EML structure was utilized in designed devices.…”