Moving beyond bulk solutions, we found that encapsulation significantly increased upconverted light output when using either ppy2 or tmd as sensitizers. ppy3, ppy2, and tmd were encapsulated with DBP into micelles to compare UC performance of micelles to TCB solutions. Although toluene is generally a better solvent for solution upconversion due to its low polarity (Fig. ), we switched the core solvent for micelle integration to TCB because it provides better solubility for sensitizers (Table ) and facilitates the formation of more consistent and stable micelles. The encapsulation process is shown schematically in Fig 2A . Freshly fabricated micelles were approximately 25 nm in diameter (Table ) allowing for facile dispersion in water to produce suspensions with excellent optical clarity. The spectroscopic characterization of these micelles is shown in Fig. , with the counts of UC and phosphorescence scaled to the highest counts of ppy3/DBP micelle UC. The concentrations of materials used for micelle integration were reoptimized for each system to maximize emitted light: the TTA-UC material concentrations required for efficient micelle fabrication were consistently higher than the optimal concentrations in toluene (Table ), indicating the importance of high solubility of the UC materials. More efficient upconverting micelles were produced by ppy2/DBP and tmd/DBP systems instead of ppy3/DBP because ppy2/DBP and tmd/DBP have higher intrinsic UC efficiencies (Fig. ) and higher solubilities in the TCB solvent used for micelle integration (Fig. ). When adding the same total quantity of UC materials, the magnitude of UCPL is lower from TCB solution than from micelles (Fig. ). Additionally, encapsulation reduced sensitizer phosphorescence (Fig. ) and increased the UC-to-phosphorescence ratio by an order of magnitude (Table ). This enhanced performance implies fewer losses from the encapsulated UC system compared to UC in TCB solution. Dramatically reduced phosphorescence has been observed in other nanoencapsulated UC systems, suggesting the generalizability of these findings. However, we note that for blue-to-UV upconversion, phosphorescence is still a significant energetic loss pathway as shown in Fig. .