阳离子交换法制备稳定的近红外区核/壳型PbS/CdS量子点
收稿日期: 2013-01-11
网络出版日期: 2013-04-17
基金资助
项目受国家自然科学基金(No. 21101151)和电工所创新人才计划(No. O940171C41)资助.
Utilizing Cation Exchange Method to Produce Core/Shell PbS/CdS Quantum Dots with Stable Infrared Emission
Received date: 2013-01-11
Online published: 2013-04-17
Supported by
Project supported by the National Natural Science Foundation of China (No. 21101151) and Program for Creative Talent in Institute of Electrical Engineering (No. O940171C41).
硫化铅量子点(PbS QDs)的光氧化稳定性差是其应用于太阳能电池等领域的主要限制因素之一. 采用阳离子交换法在合成的PbS量子点表面包裹一层具有更稳定、更大禁带宽度的硫化镉(CdS)壳层, 制备出稳定的核/壳型PbS/CdS量子点; 同时, 研究了反应温度和反应时间对阳离子交换过程的影响规律. 通过透射电子显微镜和高分辨透射电子显微镜(TEM/HRTEM)、X射线衍射仪(XRD)、吸收光谱和荧光光谱考察了所制备PbS/CdS量子点的结构、光学特性和光氧化稳定性．结果表明: 阳离子交换过程中, 离子交换反应程度有限、仅发生在量子点的表面层, 但极薄的CdS壳层已能有效钝化PbS量子点的表面缺陷、显著提高其光氧化稳定性.
李谦 , 张腾 , 古宏伟 , 丁发柱 , 屈飞 , 彭星煜 , 王洪艳 , 吴战鹏 . 阳离子交换法制备稳定的近红外区核/壳型PbS/CdS量子点[J]. 化学学报, 2013 , 71(06) : 929 -933 . DOI: 10.6023/A13010052
PbS quantum dots (QDs) have enormous potential for applications ranging from tunable infrared lasers to solar cells due to their efficient emission over a large spectral range in the infrared. Especially, multiple exciton generation has been observed in PbS QDs, which makes PbS QDs have great potential for high-efficiency solar cells. However, these applications have been limited by instability in emission quantum yield and peak position on exposure to ambient conditions. An effective strategy to improve PbS QDs' stability is overgrowth with a shell of a more stable semiconductor, such as CdS, resulting in core/shell PbS/CdS QDs. The PbS/CdS QDs were fabricated in a two-step method. In the first step, PbS QDs with a 4.8 nm diameter were prepared by using organic metal. Second, PbS/CdS QDs with 3.8 nm PbS core and 0.5 nm CdS shell were fabricated by exposing PbS QDs in Cd2+ solution for 24 h at 65 ℃. In this article, cation exchange method was adopted to moderate reaction temperature in a low temperature, so that Ostwald ripening in high temperature was avoided. The results of transmission electron microscopy (TEM) and high resolution TEM showed that PbS QDs were sphere and in a cubic cystal without obvious lattice defects. After PbS QDs being cation exchanged, PbS/CdS QDs' size and crystalline form almost kept the same. The results of X-ray diffraction also showed both the crystalline form of PbS and PbS/CdS QDs were cubic. That PbS/CdS QDs had strong absorption and bright photo fluorescence in near infrared region was proved in UV/Vis/NIR and PL spectrum. The stability was proved by comparing fresh QDs' and 3 months later QDs' PL spectrum, in which little blue shift and decrease in PL intensity was found in PbS/CdS QDs. Besides, the results showed that the degree of cation exchange was limited on the surface of the QDs. For example, 0.5 nm CdS shell was formed on the surface of PbS QDs after being exchanged for 24 h in 65 ℃. Thin as CdS shell was, it could effectively passivate PbS QDs' surface defects and significantly improve the photooxidation stability. By employing cation exchange method, highly crystallized core/shell PbS/CdS QDs with superior and stable infrared emission were fabricated at a low temperature.
Key words： PbS/CdS; quantum dots; cation exchange; core/shell QDs; stability
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