As discussed in the Introduction, one of the motivations of developing this ML calibration is fast and accurate highthroughput virtual screening (HTVS) of spectral conversion materials. The two spectral conversion techniques of interest are triplet-triplet annihilation (TTA) up-conversion and singlet fission (SF) down-conversion. In general terms, TTA involves two sensitizer molecules that absorb low-energy light and transfer their energy to a single emitter molecule which then re-emits the high-energy light. SF involves two emitter molecules, where one absorbs high-energy light and transfers half its energy to a neighboring emitter, and both re-emit lowenergy light. In such molecules, the S 1 excited state is usually involved in absorption/emission while T 1 is typically used for energy transfer. The excited state energy levels of sensitizers and emitters must be well-aligned for efficient spectral conversion -figures of merit (FOMs) to evaluate this alignment are: