Optical and electroluminescent properties of samarium complex-based organic light-emitting diodes

The optical and electroluminescent (EL) properties of newly synthesized tris(hexafluoroacethylacetonato)(phenanthroline)samarium(III)mono-methanol [Sm(hfa)3(phen)2MeOH]-based organic light-emitting diodes (OLEDs) were investigated. The as-prepared photoluminescence (PL) spectrum of Sm(hfa)3(phen)2MeOH-doped PMMA film exhibits the peaks at the wavelength around 564, 598, 645 and 710 nm which correspond to the 4G5/2 → 7H5/2, 4G7/2 → 7H7/2, 4G5/2 → 7H9/2 and 4G5/2 → 7H11/2 transitions of the Sm3+ ion, respectively. The best organic light-emitting device performance is obtained for a device using 8 wt.% Sm(hfa)3(phen)2MeOH and 40 wt.% 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4,-oxadiazole doped in poly(N-vinylcarbazole) as a emitting layer. The optimal device exhibits maximum luminance of 135 candela (cd)/m2 at the current density of 0.16 A/cm2, with current efficiency of 0.1 cd/A at the current density of 0.08 A/cm2. The EL spectrum from optimal device has the Commission Internationale De L'Eclairage (CIE) coordinate of (0.60, 0.36).