An efficient anti-Stokes photoluminescence in multi-stacked CdSe/ZnSe nanostructures with quantum dots was found under the excitation below the quantum dot ground states. The efficiency of anti-Stokes photoluminescence was equal to a few percent of the Stokes value. The dependences of anti-Stokes emission spectra upon temperature and excitation density were studied. It was shown that the excitation mechanism of this luminescence at low temperatures could be explained in terms of a 2-step 2-photon absorption process which involved deep levels of cation vacancy-related defects as intermediate states. It was found that, with increasing temperature, resonant excitation in the quantum dot photoluminescence band could occur.

Anti-Stokes Photoluminescence and Structural Defects in CdSe/ZnSe Nanostructures. M.Y.Valakh, N.O.Korsunska, Y.G.Sadofyev, V.V.Strelchuk, G.N.Semenova, L.V.Borkovska, V.V.Artamonov, M.V.Vuychik: Materials Science and Engineering B, 2003, 101[1-3], 255-8