Integration of a bulky adamantane unit with 9-phenyl-9-3,9′-bicarbazole: a novel host design for solution-processed narrowband TADF-OLEDs

To achieve high efficiency and reliability in thermally activated delayed fluorescence (TADF) and phosphorescent organic light-emitting diodes (OLEDs), developing a novel host system has emerged as a critical research theme. In this study, we synthesized CzCzPh-mAd (9-(3-((1 s ,3 s )-adamantan-1-yl)phenyl)-9 H -3,9′-bicarbazole) as a p-type host by incorporating a bulky adamantane moiety fused with three cyclohexanes into CzCzPh (9-phenyl-9 H -3,9′-bicarbazole). By incorporating a large and rigid adamantane group into the CzCzPh host ( CzCzPh-mAd ), we aimed to maintain the electrochemical and photophysical properties of CzCzPh while increasing its molecular weight, film-forming characteristics, and thermal stability. Ultimately, the solution-processed narrowband blue TADF-OLED employing the CzCzPh-mAd host exhibited a high external quantum efficiency greater than 13% and demonstrated superior thermal stability and reproducibility in device efficiency compared to devices based on CzCzPh . A p-type host, CzCzPh-mAd , incorporating a bulky and rigid adamantane group, demonstrates promising performance stability for high-efficiency solution-processed OLEDs.