Sustainable iron-catalyzed carbazole dimerization for high triplet host/electron blocking materials of efficient deep blue OLEDs

Dicarbazole (DCZ) derivatives, a class of nitrogen-containing heterocyclic polyaromatics, have gained attention for their excellent hole mobility, thermal stability, and electrochemical durability in organic optoelectronics. However, achieving both high stability and high triplet energy in one molecule remains rare, limiting blue OLED performance. To address this, an iron-catalyzed oxidative dimerization of carbazoles using air as the oxidant is developed, yielding 9H-1,9’-dicarbazole (19DCZ) via ortho-selective C–H amination. Computational studies reveal that a hydride-bridged iron dimer intermediate lowers the reaction energy barrier. 19DCZ derivatives (DCZ-1 and DCZ-2) demonstrate high efficiency as hosts and electron blocking layers in deep blue OLEDs, with EQEmax up to 22% and power efficiencies over 30 lm/W. Notably, the devices show significantly improved lifetimes, with LT60 reaching 114–118 h—over 3.5 times longer than the reference. This approach introduces a new class of high-performance materials for stable, efficient deep blue OLEDs. Dicarbazole (DCZ) derivatives are attractive for use in organic optoelectronic devices due to their hole-transporting mobility and high thermal stability. Here, iron-catalyzed synthesis is reported for various DCZs, and demonstrated for use in deep blue OLEDs.