CdSe包覆层数对水溶性CdTe/CdSe(Ⅱ型)核壳量子点的光学特性和微观结构的影响

Effects of CdSe Layer Number on the Optical Properties and Microstructures of CdTe/CdSe (Ⅱ) Core/Shell Quantum Dots

在水相合成的CdTe量子点的体系中通过分批次加入新鲜配制的NaHSe和CdCl2溶液,制备出了CdSe包覆层数不同的CdTe/CdSe核壳量子点,并着重考察了CdSe包覆层数对CdTe/CdSe核壳量子点的光学特性以及微观结构的影响.与CdTe量子点相比,CdSe单层包覆的CdTe/CdSe核壳量子点的吸收峰和荧光发射峰出现明显红移;随着CdSe包覆层数的增多,CdTe/CdSe核壳量子点吸收光谱的覆盖范围向长波方向扩展,荧光发射峰强度逐步下降,荧光寿命大幅延长,体现出Ⅱ型核壳量子点的特征.X射线衍射(XRD)分析表明,随着CdSe包覆层数的增多,CdTe/CdSe核壳量子点的粉末衍射峰由CdTe衍射峰位置逐步向CdSe衍射峰位置靠近.CdTe/CdSe核壳量子点因其延伸到近红外区域的宽吸收特性致使其在太阳电池领域具有重要的应用前景.

CdTe/CdSe core/shell quantum dots （QDs） with different numbers of CdSe layers were synthesized in aqueous media by sequentially adding freshly-prepared solutions of NaHSe and CdCl2 to a solution of CdTe QDs several times.The optical properties and microstructures of the resulting QDs were investigated.Compared with those of CdTe QDs,the optical absorption and fluorescence emission peaks of CdTe/CdSe core/shell QDs with a single CdSe layer shifted to longer wavelength.As the number of CdSe layers was increased,the optical absorption spectra of the CdTe/CdSe core/shell QDs covered a wider range and extended to longer wavelengths,the intensity of fluorescence emission decreased gradually,and the fluorescence lifetime increased significantly,consistent with the behavior of type Ⅱ core/shell QDs.Compared with those of CdTe/CdSe QDs with a single CdSe layer,the diffraction peaks of the CdTe/CdSe QDs with three CdSe layers shifted from the standard positions of CdTe diffraction peaks to those of CdSe.The CdTe/CdSe type Ⅱ core/shell QDs show promise for application in solar cells because of their broad absorption spectra that extend to longer wavelengths.