For sensitizers, the first check is if the energies are invalid, i.e. if the T 1 is greater than the S 1 . Then, molecules with S 1 close to T 1 are rated higher. Emitters can be separated into those suitable for singlet fission (singlet more than twice triplet) or triplet-triplet annihilation (singlet less than twice triplet). The same FOM formula is used for both cases, where S 1 close to twice T 1 is desirable. By ensuring the ratios are as close as possible to ideal, we ensure there is minimal loss in energy. Note that properties related to absorption-toemission likelihood such as oscillator strength, triplet-triplet energy transfer probability, triplet-triplet annihilation probability, and others are also important, but are not considered in the present analysis which focuses on optimizing excited state energy level alignment. Although not considered here, xTB-sTDA does output the oscillator strength of each transition, which can be directly used, demonstrating a further benefit of the calibration method.