Synthesis And Application Of PbS Colloidal Quantum Dots

PbS quantum dots(QDs)have the advantages of large Bohr radius(18nm),narrow band gap(0.41 e V),symmetrical band structure,good photoconductivity,large dielectric constant,wide absorption spectrum and high absorption coefficient.In recent years,the research of PbS QDs has become one of the hot spots in the field of optoelectronic materials.We know that the excellent optical properties of PbS QDs are mainly affected by the size of QDs.The range of absorption spectrum can be tuned by controlling the size of synthetic QD.Therefore,it is very important to realize the regulation of Pb S QD.In the traditional method,the size of QD can usually be controlled by the selection of parameters,such as synthesis temperature and reaction conditions,while the reproducibility of the experiments is poor.In this paper,the regulation of PbS Colloidal QDs was studied by combining femtosecond laser irradiation and the traditional method,and the effects of femtosecond laser irradiation on the optical properties of Pb S QDs were investigated.The PbS QDs synthesized by the traditional method were irradiated at different times using femtosecond laser,the absorption spectra were analyzed.From the absorption spectrum,it can be seen that the femtosecond laser irradiation with a short time will occur a tiny "blue shift",indicating that the PbS QDs with the short time of femtosecond laser irradiation will lead to the reduction of the size PbS QDs due to the explosion of coulomb,if we continue to extend the time of femtosecond laser irradiation,the size will also continue to decrease.In a conclusion,the regulation of the particle size of PbS QDs can be achieved by adjusting the irradiation time of femtosecond laser.On the other hand,the Pb S QDs respond to a wide spectral range and are well suitable for using as photodetectors.In view of this,we have produced the Schottky PbS QD photodetectors.The effects of the parameters,such as ligand exchange time,spin coating layers and annealing,on the spectral responsibilities of the detector were investigated,the optimization of device performance was carried out.The results show that the responsibility of the photodetector is the highest when the ligand-exchange time is chosen as 20 seconds,and the responsibility of the photodetector increases with the number of PbS QD layers,the annealing process can obviously improve the responsibility of the photodetectors.