NIR-OLED (1.54 µm) emitting electroluminescent diode arrays based on Er-complexes manufactured by cost-effective methods

Solution processed 1.54 μm near infrared organic light-emitting diodes (NIR-OLED) based on novel Er(III) complexes, having the general formula [Er( -diketonate)3(N,Ndonor)], have been manufactured by cost-effective methods and their properties studied. 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (Htfnb or Hnta) or 1,1,1-trifuoro-5,5-dimethyl-2,4-hexanedione (Htpm) are the fluorinated -diketonate primary sensitizers, and 2,2’-bipyridine (bipy) or 5-nitro-1,10-phenanthroline (5NO2phen) act as N,N-donors. The simple structure of the diodes is glass/indium-tin oxide (ITO)/poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)/[Er-complex]/Ca/Al. The resulting electroluminescence corresponds with the 4I13/2→4I15/2 Er(III) emission at 1.54 μm and no visible emission is observed. Photophysical characterization proves that, upon organic ligand excitation by UV light, the luminescence from the ligands is totally quenched in favour of 4I13/2→4I15/2 Er(III) emission, confirming a complete resonant energy transfer from the ligands to the Er(III) ion, analogous to that observed in the electroluminescence emission. We present a fabrication method that avoids any photolithographic or mask step. The reported results show a simple way to obtain large area NIR-OLEDs by cost-effective methods.