Researchers from National Taiwan University, together with colleagues from Yuan Ze University, National Dong Hwa University and Academia Sinica, have developed a very high efficiency blue TADF OLED device, by adopting a favorable horizontal oriented host material.
The researcher designed a new host material (4Ac26CzBz) that is made from acridan and carbazole moieties linked to a benzimidazole core. The host material exhibits a wide optical gap (Eg) and high triplet energy (T1) of 3.3 and 3.0 eV, respectively. The researchers used 4TCzBN as the blue-light TADF dopant, and report a remarkably high device external quantum efficiency of 35.8 % (59.8 cd/A and 62.8 lm/W) and a low turn-on voltage (<3 eV). The device features with significant suppression of the efficiency roll-off, maintaining a high efficiency of 29.7 % as luminance at 1000 cd/m2.
The researchers explain the excellent performance by the host’s ambipolar carrier transporting properties, which refer to its ability to transport both electrons and holes effectively, high photoluminescence quantum yield (PLQY) of 98.6 %, and highly horizontal orientation of transition dipole, as determined through diverse analytical measurements.
