Study On Preparation And Properties Of Copper And Tin Co-doped Fluorescent Quantum Dots

Quantum dots(QDs), being called semiconductor nanocrystals(d=1~10nm), are generally composed of II-VI and III-V elements(such as CdS, Cd Se, InP, etc.), and have some optical properties, such as high photoluminescence(PL) quantum yields(QYs), better stability and tunable emission wavelength. Therefore, many applications of QDs were induced such as fluorescent labeling, biochip, optoelectronic device, solar cells and so on. Compared with the non-doped QDs, the doped QDs show less self-absorption, better photochemical stability, and tunable emission with wider range. Besides, co-doped QDs can compensate the charge imbalance induced by single doping, and decrease the trap-mediated nonradiative electron-hole recombination. Therefore, co-doped QDs were widely studied by researchers recently.In this paper, we studied the optical properties of single doped QDs(CdS:Cu QDs and CdS:Sn QDs) and co-doped QDs(CdS:CuSn QDs) on the basis of experimental results from CdS QDs, characterized their PL spectra, PL QYs, UV-vis absorption spectra, morphology and structures, and discussed their luminescence and absorption mechanism. Then, single doped and co-doped CdSe QDs were also synthesized and their optical properties and structures were analyzed. The results were presented as follows:(1) We present a one-pot procedure for the synthesis of CdS, CdS:Cu and CdS:Sn QDs under the high temperature and non-oxygen condition with 1-Octadecene(ODE) organic phase system. The effects of experimental conditions including the dopant concentration and the reaction time on the properties of QDs were studied in detail. The PL QYs of CdS:Cu QDs and CdS:Sn QDs were improved efficiently. The PL QYs of CdS:Cu QDs reached as high as 13.5%, which was higher than that of CdS:Sn QDs. The PL spectra of CdS:Cu and CdS:Sn QDs both showed a red shift. Compared to CdS:Sn QDs, the PL spectra of CdS:Cu QDs could reach 690 nm, which was higher than CdS:Sn QDs.(2) We present a one-pot procedure for the synthesis of CdS:CuSn QDs under the high temperature and non-oxygen condition. The effects of experimental conditions including dopant concentration and reaction time on the properties of QDs were studied in detail. The PL QYs of CdS:CuSn QDs were significantly improved and the value were reached as high as 24.6%. Besides, The PL QYs of CdS:CuSn QDs were further improved by coating ZnS QDs(up to 38.2%). The PL spectra of CdS:CuSn QDs showed a red shift and the PL peak is near 640 nm.(3) We present a rapid injection procedure for the synthesis of CdSe QDs, single doped CdSe:Cu and CdSe:Sn QDs, and co-doped CdSe:CuSn QDs at the high temperature and non-oxygen condition. The effects of experimental conditions including dopant concentration and reaction time on the properties of QDs were studied. The PL QYs of CdSe:CuSn QDs, CdSe:Cu QDs and CdSe:Sn QDs were improved efficiently. The doping of Cu and Sn into CdSe QDs can improve the PL QYs of CdSe efficiently, and the highest PL QYs was reached as high as 14.9%. Compared with CdS:CuSn QDs, the PL spectra of CdSe:CuSn QDs showed a wider red shift and its PL peak could reach 740 nm.In conclusion, compared with single doped QDs and non-doped QDs, CuSn co-doped QDs had different optical prosperities, which can be used potentially in PL industry.