Synthesis And Photoluminescence Properties Of CuInS₂ Quantum Dots And Their Core/shell Structures

Copper indium disulfide(CuInS2)is a kind of environmentally friendly semiconductor that has plenty of advantages such as direct bandgap(1.53 eV),good biology compatibility,and high thermal stability.Quantum dots(QDs)are nanoscale materials that are spatially confined in three dimensions.The high surface to volume ratio of QDs leads to tunable luminescence properties resulting from surface characteristics,which leads to the unique physical properties of QDs.To further improve the performance of CuInS2 QDs,the core/shell QDs based on CuInS2 core QDs have been intensively studied recently.CuInS2 based core/shell QDs show enormous application potential in photovoltaic devices and biological labeling.However,the photoluminescence mechanism of the CuInS2 based QDs is still under debate owing to the complexity of their alloyed structure.In this thesis,the fabrication and luminescence properties of the CuInS2 based QDs are discussed.We synthesized the CuInS2 QDs by using the solvothermal method.The absorption and luminescence properties of the CuInS2 QDss were investigated.The origin of the wide UV-Vis absorption peak is unclear.We calculated the exciton binding energy by using the effective mass approximation method,and it agrees well with the experiment result,so the absorption peak is attributed to the exciton absorption.Besides,the luminescence properties of the CuInS2 QDs synthesized under different experimental conditions were studied.The CuInS2/ZnS core/shell QDs were prepared.We have investigated the structure and luminescence mechanism of the alloyed QDs synthesized by ZnS coating of the CuInS2 QDs.The photoluminescence spectra exhibit abnormal blue-shift with increasing excitation wavelength,which indicates that the cation exchange that occurs between the core and the epitaxial shell yields the dual-color luminescent alloyed QDs.We confirmed this by using analysis of the UV-Vis absorption spectra and the time-resolved photoluminescence spectra.We found that the heavy copper doping induces change of the absorption-tail type of the ZnS QDs.