Two new red-emitting ternary europium(iii) complexes with high photoluminescence quantum yields and exceptional performance in OLED devices

Abstract

Two new organo-europium complexes (OEuCs) [Eu(btfa)₃(Bathphen)] (OEuC-1) and [Eu(tta)₃(Bathphen)] (OEuC-2) where btfa and tta are the anions of 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 2-thenoyltrifluoroacetone while Bathphen = Bathophenanthroline have been synthesized and characterized. Both complexes in the solid state exhibit strong red emissions with photoluminescence quantum yields (PLQYs) of 80% ± 10%. These complexes were tested as dopants in the emitting layer (EML) to fabricate red organic light emitting diodes (R-OLEDs). Through device engineering involving the amalgamation of appropriate host materials and complexes, we have achieved exceptional overall R-OLED performance for an OEuC-2 based device, with maximum current efficiency (CE_max) = 9.91 cd A⁻¹, maximum power efficiency (PE_max) = 9.15 lm W⁻¹, maximum external quantum efficiency (EQE_max.) = 6.24%, brightness (B) of 545 cd m⁻², and (CIE)_x,y = 0.620, 0.323 at J = 10 mA cm⁻².