| Quantum dots are zero-dimensional materials with the advantages of tunable size,compatibility with any substrate,and low production cost.They are extremely attractive for energy,sensors,biomedicine,and flexible technology.And the application prospects of this material are very broad in the field of infrared detection.However,quantum dot materials have the disadvantage of low carrier mobility.In contrast,2D nanosheet materials have high mobility,but its spectral tunability is poor,which limits their application in photodetectors.Therefore,this thesis combines PbS quantum dots with PbS nanosheets to prepare a new type of quantum dot photodetector,and various characterization and testing methods are used to analyze and study the performance of detectors.The regulation of the absorption wavelength in the range of 1133.5nm～1562nm is to control the size of the synthesized PbS quantum dots by controlling the reaction time and ligand concentration in terms of material synthesis.PbS nanosheets are successfully prepared by pre-synthesizing Cu S nanosheets and using cation exchange method.The effects of ligand substitution,channel length,annealing,and device structure on the device are studied in detail in terms of device research.Studies show that different types of ligands make the passivation effect of quantum dots different,which leads to gaps in device performance;the use of a smaller conduction channel length is beneficial to improve device performance;appropriate annealing temperature and time are critical to the improvement of device performance;the performance of the device can be changed by tuning the device structure.On the basis of the research on photoconductive devices,bilayer PbS-NPs:PbS-CQDs junction photodetectors are fabricated and studied.The research results show that the device uses PbS quantum dots and high-mobility PbS nanosheets to construct a PN junction and a photovoltaic tunable conductive channel,which can achieve higher gain,SNR and faster response than single-layer quantum dot photoconductivity and double-layer quantum dot junction devices by reducing the recombination of photogenerated carriers while suppressing dark current.By combining the advantages of the high mobility of PbS nanosheets and the size tunability and high absorption coefficient of PbS quantum dots,this paper explores a new way to realize high-performance infrared detectors. |
