Optically upconverting liquid-filled polymeric materials that are made by curing a curable composition. The materials include a substantially liquid phase that serves to dissolve upconverting chromophores, optionally surfactants and an optionally cross-linked polymer matrix that retains or houses the liquid phase, provides mechanical stability, and offers some protection from oxygen. The optically upconverting liquid-filled polymeric materials have a phase-separated morphology. In preferred embodiments, the domains formed by the two phases are so small that light scattering is largely suppressed, which renders the upconverting liquid-filled polymeric materials largely transparent. The liquid phase provides a high mobility of the dissolved chromophores and the photophysical properties, such as the high upconversion quantum efficiency and the low excitation intensity threshold required to achieve upconversion, are thus more reminiscent of conventional or oxygen-free solutions than polymeric solids. These photophysical properties can be achieved by preparing the polymers under oxygen-free or, in preferred embodiments, under ambient conditions. The design principle introduced here to create upconverting liquid-filled polymeric materials is versatile and general; the liquid phase, the surfactants, the polymer matrix, and the upconverting chromophores can all readily be varied. Importantly, the optically upconverting liquid-filled polymeric materials can be prepared in a one-step process, which makes them preferable over other liquid-containing polymers that enable upconversion.