Enhanced near infrared electroluminescence from a neodymium complex in organic light emitting diodes with a solution processed exciplex host
We report enhanced near infrared (NIR) electroluminescence from a Nd3+ complex with thenoyltrifluoroacetone and 1,10 phenanthroline ligands. The NIR emitting complex was blended into an exciplex forming co host system comprising 2,7 bis(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 Nd3+ complex molecules. Efficient energy transfer from the singlet and triplet exciplexes formed between the host molecules to the Nd3+ 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/cm2, due.