The present invention provides phosphor inks configured to achieve high efficiency in converting LED light from one wavelength to another. The phosphor ink composition for deposition on an LED device comprises a phosphor component having nano-phosphor particles on the order of 100 to 1000 nanometers, and a curable resin component. In particular, the nano-phosphor particles are uniformly dispersed throughout the ink composition. The nano-phosphor particles may be formed by a size reduction process carried out on larger phosphor particles on the order of 1 to 50 micrometers. Preferably, the size reduction process is based on solvent wet milling. Methods for preparing the phosphor inks based on forming the nano-phosphor particles from larger particles by solvent wet milling are also provided.