Highly luminescent pure-red-emitting fluorinated β-diketonate europium(III) complex for full solution-processed OLEDs

Current manufacturing technologies for OLEDs involve the use of expensive high vacuum techniques and call for thermal stability requirements which are not fulfilled by many materials. These problems disappear when the OLED films are deposited directly from solution. In this study, we have designed, synthesized and characterized a novel octacoordinated complex, Tris(1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedionate)mono(bathophenanthroline) europium(III), to be used as a >complex-only> emissive layer in wet-processed OLEDs. Upon excitation in the UV region, very efficient energy transfer from the ligands to Eu3+ takes place, giving rise to intense red emission with very high monochromaticity (R=19), both in powder and as a thin film. The decay times of 754 μs (powder) and 620 μs (thin film) are comparable to those of the most efficient Eu3+ β-diketonate complexes reported to date. The same energy transfer leading to saturated red and narrow emission is also observed in the OLED device (glass/ITO/PEDOT:PSS/[Eu(cbtfa)3(bath)]/Ca/Al) when biased at >5.2 V. Its high quantum efficiency (∼60%), good thermal stability up to 200 °C and adequate thin film forming properties make this material a promising chromophore for cost-effective OLEDs.P. Martín-Ramos thanks Fundación Iberdrola for its financial support. CEMDRX group is grateful to Fundação para a Ciência e a Tecnologia (FCT) for providing funds under grant PTDC/FIS/102284/2008 and PEst-C/FIS/UI0036/2011. Funding by the Spanish Ministerio de Economía y Competitividad (MINECO) under projects MAT2012-37276-C03 and MAT2012-37276-C01 is gratefully acknowledged by the URJC and ICMM groups