Research On Optoelectrical Properties Of Novel Nano-structured Materials Based On Ⅱ-Ⅵ Compound Semiconductors

Ⅱ-Ⅵ compound semiconductors with the properties of wide and direct band-gap and large excitation binding energy are a group of important semiconducting materials, and show wide applications in light-emitting diodes, solar cells, laser devices, and so on. Compared to the corresponding bulk materials, nanomaterials possess novel properties due to the quantum confinement effect. Ⅱ-Ⅵ inorganic/organic hybrid semiconductors orderly composed of Ⅱ-Ⅵ inorganic layers and orgaic ligands are a unique family of bulk materials with layered nanostructures. Ⅱ-Ⅵ compound quantum dots (QDs) have the size-dependent optical and photoluminescent emission properties. The fabrication of core/shell heterostructures is an effective route for designing novel kinds of QDs, tuning the properties of QDs, and improving the stability of QDs.In the first part of the current work, the inorganic/organic hybrid semiconductor2D-[Zn2S2(ha)] was prepared by the solvothermal method, in which Zn salts and sulfur powder were used as the reatants, and n-hexylamine (ha) was served as the reactive solvent. A series of inorganic/orgaic hybrid semiconductors were prepared by the same solvothermal method through doping this hybrid with Cd, Mn, and Cd and Mn, respectively, which optical absorption and photoluminescent emission properties can be tuned by changing the dopant amount. Consequently, several inorganic/organic semiconductors including Cd doped2D-[Zn2-2XCd2XS2(ha)], Mn doped2D-[Zn2-2yMn2yS2(ha)], and Cd and Mn co-doped2D-[Zn2-2x-2yCd2XMn2yS2(ha)] that directly emit white light have been obtained, which have potential applications in white light-emitting diodes.In the second part of this work, CdTe/CdSe core/shell QDs with different CdSe layers were synthesized in aqueous media by adding freshly-prepared NaHSe solution and CdCl2solution in sequence into the solution of CdTe QDs for several times, and their optical properties and microstructures were investigated and characterized, respectively. Compared with those of the CdTe QDs, the optical absorption peak and the fluorescence emission peak of the CdTe/Cdse core/shell QDs with single CdSe layer shift to longer wavelength. With the increase in the number of the CdSe layer, the optical absorption spectrum of the CdTe/Cdse core/shell QDs covers a wider range extending to longer wavelength, and the intensity of their fluorescence emission peak decreases gradually, whereas the fluorescence lifetime increases remarkably, showing the characteristics of type Ⅱ core/shell QDs. The CdTe/CdSe type Ⅱ core/shell QDs have promising applications in solar cells duo to their wide absorption spectrum extending to long wavelength.