Preparation of PbS-coated CdTe Nanocrystals through Sonochemical Reaction

Semiconductor nanoparticles have attracted much attention in recent years owing to their unique properties depending on size, shape, and various material compositions. One of the most important materials among them is cadmium telluride (CdTe), which has direct band gap of 1.5 eV and an excitonic Bohr radius of 7.3 nm. Also, high photoluminescence (PL) quantum efficiency of CdTe nanoparticles makes them an interesting material for their uses such as light emitting devices, photovoltaic and photoelectrochemical devices, and biological labels. Many semiconductor quantum dots have been tried for their applications to develop cheap and high efficient solar cell, in which suitable band gap is essential to get high efficiency. However, the quantum dots were found to have some difficulty in securing a proper band gap for solar cell since as materials size gets smaller, the materials' band gap increases in general. In this regard, coating a low band gap material onto the QDs was adopted and Hens et al. reported PbTe-CdTe particles with a core-shell structure