This review traces the development of multiresonant thermally activated delayed fluorescence (MR-TADF) molecules from benzophenone through direct heteroatom fusion, including derivatives like acridone, xanthone, and thioxanthone. It covers their photophysical and device architecture properties of benzophenone, fused benzophenone, and extended fused benzophenone derivatives. Despite promising advances, MR-TADF materials with a single carbonyl group remain underexplored, requiring further investigation into their fundamental mechanisms and practical applications. Given its vast potential, research into extended fused benzophenone-based materials continues to be a highly compelling avenue for future innovations in organic optoelectronics.

Carbonyl-containing derivatives have emerged as powerful candidates for room-temperature phosphorescence and thermally activated delayed fluorescence (TADF) due to their ability to harness both singlet and triplet excitons, enabling high device efficiency and exceptional color purity. In this review, the evolution of multiresonant TADF (MR-TADF) molecules derived from benzophenone through direct heteroatom fusion (e.g., acridone, xanthone, thioxanthone) is explored. While benzophenone holds great promise as a TADF emitter, its structural flexibility often leads to nonradiative energy loss. To address this, fused benzophenone derivatives have been developed to enhance TADF performance; however, their intrinsic rigidity presents challenges in achieving blue emission due to the planar nature of the acceptor core. Notably, extended fused-benzophenone structures containing a single carbonyl group have shown remarkable potential for MR-TADF applications. This review highlights key design strategies for engineering TADF and MR-TADF emitters based on benzophenone frameworks. It is critically examined how functional properties are influenced by carbonyl or heteroatom fusion, revealing that the incorporation of oxygen, nitrogen, or sulfur leads to rigid TADF-active emitters, while additional carbonyl fusion enables the development of narrow-band MR-TADF emitters. These insights pave the way for next-generation organic light-emitting materials with superior performance.