This review discusses the development of thermally activated delayed fluorescence (TADF) materials for organic light-emitting diodes (OLEDs). TADF materials are promising for achieving 100% internal quantum efficiency (IQE) by harvesting both singlet and triplet excitons. Unlike phosphorescent materials, which rely on heavy metals, TADF materials are purely organic, avoiding the issues associated with heavy-metal-based complexes. The key to TADF performance is a small singlet-triplet energy gap (ΔE_ST), which enables reverse intersystem crossing (RISC) to convert triplet states back to singlet states, allowing for delayed fluorescence. The efficiency of TADF emitters is influenced by factors such as the structure of the emitter, the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and the energy levels of the frontier molecular orbitals in the device. TADF emitters have been shown to achieve high external quantum efficiencies (EQEs) in OLEDs, with some devices reaching over 30%. The review highlights the development of various TADF emitters, including blue, green, yellow, orange-red, and white OLEDs, and discusses their performance in terms of efficiency, color, and stability. The use of TADF emitters as hosts in OLEDs is also explored, as well as the role of exciplex systems in demonstrating the TADF phenomenon. The review concludes that TADF materials represent a significant advancement in OLED technology, offering a promising alternative to phosphorescent materials for achieving high-efficiency, low-cost lighting and display applications.This review discusses the development of thermally activated delayed fluorescence (TADF) materials for organic light-emitting diodes (OLEDs). TADF materials are promising for achieving 100% internal quantum efficiency (IQE) by harvesting both singlet and triplet excitons. Unlike phosphorescent materials, which rely on heavy metals, TADF materials are purely organic, avoiding the issues associated with heavy-metal-based complexes. The key to TADF performance is a small singlet-triplet energy gap (ΔE_ST), which enables reverse intersystem crossing (RISC) to convert triplet states back to singlet states, allowing for delayed fluorescence. The efficiency of TADF emitters is influenced by factors such as the structure of the emitter, the overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and the energy levels of the frontier molecular orbitals in the device. TADF emitters have been shown to achieve high external quantum efficiencies (EQEs) in OLEDs, with some devices reaching over 30%. The review highlights the development of various TADF emitters, including blue, green, yellow, orange-red, and white OLEDs, and discusses their performance in terms of efficiency, color, and stability. The use of TADF emitters as hosts in OLEDs is also explored, as well as the role of exciplex systems in demonstrating the TADF phenomenon. The review concludes that TADF materials represent a significant advancement in OLED technology, offering a promising alternative to phosphorescent materials for achieving high-efficiency, low-cost lighting and display applications.