A new side-chain polymer (X-TPACz) bearing hole-transporting pendant groups accompanying a thermally crosslinkable entity was synthesized using N-([1,1′-biphenyl]-4-yl)-N-(4-(9-(4-vinylbenzyl)-9H-carbazol-3-yl)­phenyl)­bicyclo­[4.2.0]­octa-1­(6),2,4-trien-3-amine (6) via addition polymerization. The X-TPACz could be spontaneously crosslinked without using any further reagents and showed a good film-forming property upon low-temperature thermal treatment. The thermal curing temperature for the X-TPACz film was optimized to be 180 °C based on a differential scanning calorimetry thermogram. Moreover, the thermal degradation temperature of X-TPACz measured to be over 467 °C using thermogravimetric analysis demonstrated that it shows excellent thermal stability. In particular, X-TPACz exhibits the highest occupied molecular orbital (HOMO) energy level to be −5.26 eV, which is beneficial for facile hole injection and transportation. Consequently, the thermally activated delayed fluorescence organic light-emitting diodes fabricated using X-TPACz as the hole-transporting material showed state-of-the-art performances with a low turn-on voltage (V on) of only 2.7 V and a high external quantum efficiency (EQE) of 19.18% with a high current efficiency (CE) of 66.88 cd/A and a high power efficiency (PE) of 60.03 lm/W, which are highly superior to those of the familiar poly­(9-vinylcarbazole) (PVK)-based devices (V on = 3.9 V, EQE of 17.42%, with CE of 58.33 cd/A and PE of 33.32 lm/W). The extremely low turn-on voltage and high EQE were found to be due to the higher-lying highest occupied molecular orbital energy level (E HOMO = −5.23 eV) and better hole-transporting property of X-TPACz than those of PVK.

A new photocrosslinkable PX2Cz was successfully synthesized and used as an excellent hole transport material in green TADF-OLED.

The D–A–D′-type novel organic material APC was designed and synthesized as a host for TADF emitters. APC realized an external quantum efficiency of 24.0% and also retained 23.1 and 21.7% at high brightness of 500 and 1000 cd m−2, respectively.

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