Acta Chimica Sinica ›› 2013, Vol. 71 ›› Issue (06): 929-933.DOI: 10.6023/A13010052 Previous Articles     Next Articles



李谦a,b, 张腾c, 古宏伟a, 丁发柱a, 屈飞a, 彭星煜a, 王洪艳a, 吴战鹏b   

  1. a 中国科学院电工研究所应用超导重点实验室 北京 100190;
    b 北京化工大学材料科学与工程学院 北京 100029;
    c 中国科学院电工研究所超导电力科学技术研究发展中心 北京 100190
  • 投稿日期:2013-01-11 发布日期:2013-04-17
  • 通讯作者: 张腾,;古宏伟,;
  • 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

Li Qiana,b, Zhang Tengc, Gu Hongweia, Ding Fazhua, Qu Feia, Peng Xingyua, Wang Hongyana, Wu Zhanpengb   

  1. a Key Laboratory of Applied Superconductivity, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190;
    b College of Material Science and Engineering, Beijing University of Chemical Technology, Beijing 100029;
    c Center for Superconducting Power Technology, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190
  • Received:2013-01-11 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).

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