Efficient green OLEDs achieved by a terbium(III) complex with photoluminescent quantum yield close to 100

Electroluminescence of f-f transition lanthanide complex is a traditional topic for display over decades. Here we report highly efficient organic light-emitting diodes based on a new terbium(III) complex with novel ligand CPMIP (1-(4-cyanophenyl)-3-methyl-4-isobutyryl-pyrazoline-5-one). The high triplet energy level of CPMIP (3.0 eV) and inhibited quenching effects in the solid-state lead to a nearly 100% photoluminescent quantum efficiency of Tb(CPMIP)3. The best Tb(CPMIP)3 device exhibited maximum external quantum efficiency up to 19.7%, setting a new record of OLEDs based on f-f transition lanthanide complexes.