Solution processable carbazole-benzophenone derivatives as bipolar hosts enabling high-efficiency stable green TADF organic LEDs

Abstract

Solution-processable bipolar materials acting as hosts, soluble in common organic solvents, are key materials for thermally activated delayed fluorescence (TADF) emitters.

Recent endeavors and perspectives in developing solution-processable host materials for thermally activated delayed fluorescence organic light-emitting diodes

“…Grigalevicius et al demonstrated two new carbazole-benzophenone derivatives ( BPBCzO and BCzBCzO ) as bipolar hosts, employing carbazole as an electron donor and benzophenone as an electron acceptor (Scheme 3). 29 The E T of the host materials ( BPBCzO and BCzBCzO ) was 2.64 and 2.60 eV, respectively. BCzBCzO showed higher thermal stability than BPBCzO because of its higher molecular weight.…”

“…The design strategies, photophysical properties and electroluminescent performance data of solution-processed small molecule hosts are discussed below. 19–31…”

“…15–23 Solution processing is highly advantageous over vacuum processing owing to the easy processability and usage of low-cost instruments such as spin-coating, blade-casting, and inkjet printing in the former, while avoiding harsh fabrication conditions such as high temperature and pressure. Despite significant progress in the development of solution-processed OLEDs, 24–66 their efficiency and lifetimes still lag behind those of vacuum-processed devices.…”

“…Considering these challenges, small molecules, 19–31 sp 3 -cored non-conjugate linker-based dendrimers, 32–37 and polymers 38–42 with a high E T and good solubility have been demonstrated as host materials for solution-processable TADF OLEDs. Several host materials consisting of D–A, D–A–D, or D–A–D′-type architectures have been reported.…”

“…Several host materials consisting of D–A, D–A–D, or D–A–D′-type architectures have been reported. 19–42 However, these architectures can undesirably augment charge transfer between the donor and acceptor entities and extend the conjugation length, which hinders the achievement of a high E T . Although the synthesis and purification of small molecules is easier than that of polymeric hosts, it is sometimes difficult to achieve a high E T in the solid state with the former.…”