Study On The Photoelectric Characteristics And Sensitization Process Of Lead Sulfide Thin Films Prepared By Chemical Bath Deposition

Near-infrared(780-2526 nm)photodetectors have a wide range of applications in infrared imaging,security monitoring,aerospace and other fields because of their ability to work better than visible light in certain environments.Lead sulfide material has the advantages of suitable detection band,good performance,and room temperature operation.It is a very important semiconductor material in the field of near infrared photoelectric detection.At present,a variety of mature PbS thin film preparation technologies have been developed and applied.Among them,the chemical bath deposition method is widely used in the field of PbS thin film preparation because of its flexible film formation,low cost,simple operation,uniform film formation and low temperature process.In order to further improve the photoelectric performance of PbS thin films deposited by chemical bath deposition,it is usually necessary to sensitize the thin films using semiconductor material recombination,atmosphere doping and other means.PbS colloidal quantum dots have unique size effect,quantum confinement effect,and good compatibility with the energy band and lattice of PbS thin film,which is an excellent semiconductor nanocrystal sensitizing material.In this paper,on the basis of optimizing the chemical bath deposition of PbS photosensitive film and improving the surface passivation process of PbS quantum dots,the photoelectric performance of PbS photosensitive film is improved by using quantum dot sensitization process.And we had further discussed the performance change law and sensitization mechanism of the sensitization process.In this paper,the chemical bath deposition method was used to prepare PbS photosensitive films under different thiourea concentrations firstly.At the same time,the microscopic characteristics and detector performance parameters were characterized and tested with the help of various characterization methods and special photoelectric test systems,and the effect of urea concentration on the micro-morphology and photoelectric performance of the film was further studied.The results of the study indicate that an increase in the concentration of thiourea will result in an increase in film thickness,a decrease in grain size,and a preferential growth of(200)crystal planes.The devices prepared under high thiourea concentration conditions have greater photocurrent and better photoelectric performance.Under 970 nm infrared light,their responsivity and specific detection rate were 39.18 m A/W and 1.81×10¹⁰ Jones,respectively.The photoelectric properties and surface defect state density of quantum dots have greatly affected the sensitization effect of the sensitization process.This article next explores the passivation process of PbS quantum dots composite halogens with different mass fractions of CTAB/Pb I₂ ligands and the mechanism of performance changes after passivation.After the passivation process,the quantum dots were spin-coated into a film and prepared into a photodetector device.Various characterization and testing methods were used to characterize the thin film morphology and photoelectric performance of the device.The results of the device performance show that we obtained the best device performance of the PbS quantum dot device under the passivation process of 10%CTAB/Pb I₂ composite halogen ligand.Its responsivity and specific detection rate were 160.10 m A/W and 1.15×10¹² Jones,at the same time,we also analyzed the reason why the device performance varies non-monotonically with the CTAB mass score from the perspective of dark resistance and photoelectric gain.At the end of this paper,PbS quantum dots were used to sensitize the PbS photosensitive film.PbS photodetectors under different sensitization processes were prepared by spin-coating quantum dot films with different concentrations on the PbS photosensitive film.Characterization and test results show that the quantum dot sensitized device with a concentration of 100 mg/m L has the best performance,and its responsivity and specific detection rate are 53333 m A/W and 8.02×10¹¹ Jones,respectively.Compared with the unsensitized device,its performance is improved to 1.22 times and 3.02 times.Further,we also explained the sensitization mechanism of quantum dot sensitized devices and the effect of quantum dot concentration on device performance through two aspects:interface band structure and device surface morphology.