Size Distribution Control Of PbS(e) QDs And Preparation Of Their Core-shell Structure

PbSe and PbS quantum dots(QDs)have been widely studied by many researchers because of their multiple exciton generation effect,high photosensitive absorption and near infrared emission.The properties of QDs strongly depend on their size;therefore,monodispersity is a basic requirement for the preparation of high performance devices based QDs.Cation exchange is a method widely used in the synthesis of PbSe and PbS QDs.The QDs synthesized by cation exchange usually have a good performance due to the passivation of metal cation and the halide anion.However,it is still challenging to control the size distribution of QDs using this method.In view of the above,my thesis has done a lot of research on the control of size distribution of PbSe and PbS QDs.The main results are as follows:1.In this paper,a new strategy for narrowing the size distribution of colloidal QDs was developed by combining cation exchange and quantized Ostwald ripening,the key to the implementation of the scheme is to find suitable precursors of selenium(or sulfur).2.We have studied the control of the size distribution of the QDs by injecting different molecular precursors(TOPS(e),TBPS(e))and QDs precursor(CdS(e)QDs).It was found that only the injection of small QDs precursor(CdS(e))could optimize the size distribution very well.We have synthesized a series of monodisperse PbSe and PbS QDs by using this method,and the QDs were characterized by means of infrared absorption,TEM,XPS and size distribution.3.We analyzed the reaction mechanism and explored the particle size of the CdS(e)QDs which could play a regulatory role in the reaction.4.Using this strategy,we synthesized a series of monodisperse PbSe/PbS core shell QDs,and the QDs were characterized by means of infrared absorption and FTEM.The first absorption peak of the largest QDs is 2150 nm.