Full-color emission from In ₂S ₃ and In ₂S ₃:Eu ³⁺ nanoparticles

New observations on the luminescence of In ₂S ₃ and europium-doped In ₂S ₃ nanoparticles show a green (510 nm) emission from In ₂S ₃ and In _1.8Eu _0.2S ₃ nanoparticles while a blue (425 nm) emission is observed from In _1.6Eu _0.4S ₃ nanoparticles. Both the blue and green emissions have large Stokes shifts of 62 and 110 nm, respectively. Excitation with longer-wavelength photons causes the blue emission to shift to a longer wavelength while the green emission wavelength remains unchanged. The lifetimes of both the green and blue emissions are similar to reported values for excitonic recombination. When doped with Eu ³⁺, in addition to the broad blue and green emissions, a red emission near 615 nm attributed to Eu ³⁺ is observed. Temperature dependences on nanoparticle thin films indicate that with increasing temperature, the green emission wavelength remains constant, however, the blue emission shifts toward longer wavelengths. Based on these observations, the blue emission is attributed to exciton recombination and the green emission to Indium interstitial defects. These nanoparticles show full-color emission with high efficiency, fast lifetime decays, and good, stability; they are also relatively simple to prepare, thus making them a new type of phosphor with potential applications in lighting, flat-panel displays, and communications.