Extended Data Fig. shows how for a given figure of merit, each order of magnitude change in gTT leads to an order of magnitude change in J90. Extended Data Fig. shows the potential interplay between TTA and STA. The J90 value behaves nearly linearly with 𝑘 r S 𝐾 eq when only TTA is considered (red dots, the slope is 2 ). It is also a useful strategy to seek materials with high 𝑘 ! " (providing kRISC/kISC is not reduced), which is also the underlying physics for hyperfluorescent OLEDs 42 . At the same time, there is a need to understand which process dominates the efficiency roll-off. Whilst all major annihilation processes scale with the triplet population and thus inversely with our proposed FOM, the dominance of these processes in each OLED is not sufficiently known. Therefore, there is a need to measure both gST and gTT in a wider set of devices to fully understand how emitter kinetics need to be engineered to reduce efficiency roll-off.