Indolocarbazole Derivatives for Highly Efficient Organic Light‐Emitting Diodes

Abstract Since the discovery of the organic light‐emitting diode (OLED), scientists worldwide have dedicated extensive efforts to enhance the efficiency and reliability of devices, striving for superior performance. Various molecular structures have undergone structural modifications to assess their suitability in achieving the desired outcomes. This review focuses on indolo[3,2,1‐ jk ]carbazole (ICz), a building block that has garnered considerable attention within the OLED community. The rigid and fused ICz core induces a multiresonance effect through an alternating distribution of frontier molecular orbitals. Notably, ICz‐based thermally activated delayed fluorescence emitters exhibit a full width at half maximum below 20 nm, ensuring high color purity, and boast an external quantum efficiency above 30%, comparable to state‐of‐the‐art narrow‐emitting boron–nitrogen‐type materials. Furthermore, the ICz core is a building block in host and metal complexes, enhancing stability, efficiency, and color purity. Consequently, the ICz core is promising as a central component in host and emitters, improving OLED device performance. This review aims to succinctly summarize studies on ICz‐based organic materials within the OLED field, offering insights into future perspectives regarding developing and applying ICz‐derived organic compounds.