Room Temperature Synthesis of HgTe Quantum Dots in an Aprotic Solvent Realizing High Photoluminescence Quantum Yields in the Infrared

A computer controlled, automated synthesis method has been used to grow HgTe quantum dots (QDs) entirely at room temperature, using an aprotic solvent, dimethyl sulfoxide. The growth is carried out with small iterative additions of the Te precursor, which allows frequent sampling of the products to assess the growth trajectory in terms of the relationship between the QD concentration and QD diameters as the reaction proceeds. As such, this approach is a useful tool to develop a detailed understanding of the growth process and to work toward optimizing the reaction conditions in terms of the quality of the resulting QDs. HgTe QDs with emission spectra ranging up to 3000 nm and with photoluminescence quantum yields of up to 17% at 2070 nm have been produced by this method. Although coupling of the exciton to ligand vibrations is inevitable in this energy range, attention to the growth conditions and QD quality can influence the detailed coupling mechanisms, with fewer carrier traps reducing the extent of polaron mediated coupling. The influence of reaction conditions such as ligand-to-cation ratios and rate of Te precursor addition upon the onset of QD aggregation has been also examined. The method is readily up-scalable and has been employed to produce HgTe QD materials for infrared photodetectors.