Indolo[3,2-b]carbazole is a polycyclic aromatic heterocycle consisting of fused indole and carbazole units. This rigid, planar, and electron-rich structure endows it with excellent hole-transporting properties, high thermal stability, and good photophysical characteristics. Its primary and most significant application is in the field of organic electronics, particularly as a fundamental building block for organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). It serves as a core unit for constructing high-performance hole-transporting materials (HTMs), host materials for phosphorescent emitters, and as a component in donor-acceptor type polymers for solar cells. Derivatives of indolo[3,2-b]carbazole are extensively researched for use in display and lighting technologies due to their ability to improve device efficiency and longevity. While its core application is material science-oriented, its well-defined and synthetically modifiable structure also makes it a valuable intermediate for researchers developing novel organic semiconductors. Its properties are crucial for advancing next-generation optoelectronic devices.