PNNL

Abstract

Efficient upconversion luninescence is observed from CdTe nanoparticles in solution and precipitated as solids. In the solids, the upconversion luminescence spectrum is significantly red-shifted relative to the normal photoluminescence, whereas in solution, there is very little spectral shift. The upconversion luminescence exhibits a near quadratic laser power dependencem, both at room temperature and at 10K. Both the upconversion and photoluminescence show similar decay dynamics with the solid samples showing shorter lifetimes compared to the solutions. This lifetime shortening is attributed to surface states is the likely upconversion excitation mechanism in these particles and that phonon populated defeat do not contribute to the upconversion.