π‐Extended Carbazole Derivatives as Host Materials for Highly Efficient and Long‐Life Green Phosphorescent Organic Light‐Emitting Diodes

High-performance organic light-emitting diodes (OLEDs) that use phosphorescent and/or thermally activated delayed fluorescence emitters are capable of realizing 100 % electron-to-photon conversion. The host materials in these OLEDs play crucial roles determining OLED performance. Carbazole derivatives frequently used as materials, among which 3,3-bis(9H-carbazol-9-yl)biphenyl (mCBP) is often for lifetime testing scientific studies. In this study, the π conjugation carbazole unit was expanded to enhance by designing and developing two benzothienocarbazole (BTCz)-based namely m1BTCBP m4BTCBP. Among formed a highly efficient [Ir(ppy)3]-based with an operational luminescence half-life (LT50) over 300 h at initial luminance approximately 12000 cd m−2 (current density: 25 mA cm−2). LT50 value 1000 cm−2 estimated be about 23 000 h. This performance clearly higher than mCBP-based (LT50≈8500 h).