A new, highly luminescent terbium complex (see Figure) is investigated here as a material for organic light‐emitting diodes (OLEDs). It is demonstrated that device efficiencies of over 2.6 lm/W are possible—the highest yet reported for a lanthanide‐based OLED. This indicates that lanthanide‐based materials are a viable alternative to Alq‐ and PPV‐based polymers for use in commercial OLED displays.

Divalent molecular lanthanide complexes are shown to offer promise as tunable light emitting materials in thin film electroluminescent displays for the first time in this study. Bright orange luminescence is obtained from thin film EL device structures containing bis[tris(dimethylpyrazolyl)borate]europium(II) (1), which has a high quantum efficiency in the solid state. The effect of device structure upon device efficiency and light purity is discussed and an optimum EL device structure for 1 detailed.

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