A multifunctional bipolar host material based on phenanthroimidazole for efficient green and red PhOLEDs with low turn-on voltage

Bipolar blue or deep-blue emitting materials are particularly effective to achieve high-performance full color OLEDs. In this study, a novel deep-blue bipolar fluorophore, PPI-F-Cz was designed and synthesized by attaching an electron-withdrawing chromophore phenanthro[9,10-d] imidazole (PI) and an electron-donating group carbazole to the sp(3)-hybridized C-9 atom of the fluorene. Profiting from balanced carrier mobility, the molecule shows high photoluminescence (PL) and electroluminescence (EL) efficiencies. Using PPI-F-Cz as a non-doped emitting layer (EML), an organic light-emitting device exhibits high performance with CIE color coordinates of (0.155, 0.055), a maximum external quantum efficiency (EQE) of 4.64%, current efficiency (CE) of 7.68 cd/A, and power efficiency (PE) of 8.04 lm/W. Additionally, equipped with the bipolar transport properties and high triplet energy (2.40 eV), PPI-F-Cz was allowed to be used as an efficient host for green and red PhOLEDs with the maximum EQEs of 16.83% and 20.98%, CEmax of 58.47 cd/A and 25.19 cd/A, PEmax of 53.66 lm/W and 23.28 lm/W respectively.