Initially, we characterized the UC properties of the iridium complexes ppy2 and tmd with a single annihilator, 2,7-di-tert-butylpyrene (DBP) in toluene, which is a favorable nonpolar solvent for screening TTA-UC. The UC properties of the ppy3/DBP system were also measured to serve as a reference. All three iridium complexes displayed similar absorption ranges and emission profiles with slightly red-shifted emission peaks from ppy3 to ppy2 to tmd, suggesting that ppy2 and tmd should also possess energetically favorable properties for blue-to-UV UC (Fig. ). Fig. presents the normalized UC photoluminescence (UCPL) of the three sensitizers. Each sensitizer is paired with DBP in toluene under 447 nm excitation with varying power densities. The sensitizer concentrations in this experiment were optimized to maximize UCPL (Table ), and the DBP concentration was held constant between the three systems to maintain consistency and to minimize self-absorption effects from DBP. All UCPL spectra had identical shapes when compared to photoluminescence of DBP (335 nm excitation, Fig. ). The spectral shape of the UC emission remained consistent across excitation power densities. We quantified the UC quantum yield (ΦUC) (Equation ) of these systems as: 60