This article presents a study on efficiency roll-off in thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). Efficiency roll-off refers to the decrease in efficiency as the drive current increases. The authors analyze a wide range of TADF OLEDs and find that neither the energy difference between singlet and triplet excited states (ΔE_ST) nor the rate of reverse intersystem crossing (k_RISC) fully account for the efficiency roll-off. They propose a new figure of merit (FOM) for materials design to reduce efficiency roll-off, which considers the dynamic equilibrium between singlets and triplets in TADF materials. The FOM is defined as k_r^S * K_eq, where k_r^S is the radiative rate constant for singlet states and K_eq is the equilibrium constant between singlet and triplet states. The study shows that this FOM has a stronger correlation with J_90 (the current density at which the external quantum efficiency falls to 90% of its peak value) than k_RISC alone. The authors also discuss the importance of minimizing triplet population to reduce efficiency roll-off and highlight the role of bimolecular processes such as triplet-triplet annihilation (TTA) and singlet-triplet annihilation (STA) in this context. The study concludes that the proposed FOM provides a better predictor of efficiency roll-off than previous approaches and offers a new strategy for the design and development of TADF materials. The results suggest that future TADF materials should focus on maximizing the FOM to achieve lower efficiency roll-off and improve the performance of TADF OLEDs in practical applications.This article presents a study on efficiency roll-off in thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs). Efficiency roll-off refers to the decrease in efficiency as the drive current increases. The authors analyze a wide range of TADF OLEDs and find that neither the energy difference between singlet and triplet excited states (ΔE_ST) nor the rate of reverse intersystem crossing (k_RISC) fully account for the efficiency roll-off. They propose a new figure of merit (FOM) for materials design to reduce efficiency roll-off, which considers the dynamic equilibrium between singlets and triplets in TADF materials. The FOM is defined as k_r^S * K_eq, where k_r^S is the radiative rate constant for singlet states and K_eq is the equilibrium constant between singlet and triplet states. The study shows that this FOM has a stronger correlation with J_90 (the current density at which the external quantum efficiency falls to 90% of its peak value) than k_RISC alone. The authors also discuss the importance of minimizing triplet population to reduce efficiency roll-off and highlight the role of bimolecular processes such as triplet-triplet annihilation (TTA) and singlet-triplet annihilation (STA) in this context. The study concludes that the proposed FOM provides a better predictor of efficiency roll-off than previous approaches and offers a new strategy for the design and development of TADF materials. The results suggest that future TADF materials should focus on maximizing the FOM to achieve lower efficiency roll-off and improve the performance of TADF OLEDs in practical applications.