A simple bipolar host material based on triphenylamine and pyridine featuring σ-linkage for efficient solution-processed phosphorescent organic light-emitting diodes

Solution-processable host materials play an important role in achieving highly efficient and cost-effective phosphorescent organic light-emitting diodes (PhOLEDs). This paper designed and prepared a simple solution-processable host material of TPA-PyF2 based on triphenylamine and pyridine to fabricate efficient solution-processed PhOLEDs. TPA-PyF2 featured an σ-linkage between the electron donor and acceptor units, which not only served to limit the conjugation length of the molecule and maintain a high triplet energy level, but also endowed the host molecule with a three-dimensional structure to enable high film morphological stability for solution processing. As a result, TPA-PyF2 exhibited a high triplet energy level (2.82 eV), high thermal stability, bipolar charge transfer, and excellent film morphology. Blue solution-processed OLED with a simple double-layer structure based on TPA-PyF2 host achieved a maximum current efficiency, power efficiency, and luminance of 17.2 cd/A, 7.1 lm/W, and 11519 cd/m2, respectively, with a small efficiency roll-off of only 9.1% at the practical luminance of 1000 cd/m2. This work reveals that the σ-linkage strategy is promising in designing efficient solution-processable host materials for high-efficiency PhOLEDs.