Research On Near Infrared Photodiode Based On Lead Sulfide Quantum Dots

The energy band of the lead sulfide crystal is 0.41eV,and can detect infrared radiation with a wavelength of 3?m,which makes PbS a commonly used near-infrared detector material.When the particle size of lead sulfide crystals is reduced to a few to several tens of nanometers,similar to its Bohr radius,its energy level is separated due to the quantum confinement effect and produces a series of peculiar photoelectric effects:high extinction coefficient,the absorption peak increases as the quantum dot size becomes smaller,and a broad absorption spectrum.The lead sulfide quantum dots are considered by the researchers as a new generation of near-infrared detector materials due to their simple manufacturing method,low cost and high detection sensitivity.The main content of this paper is the preparation and optimization of near-infrared photodiodes based on lead sulfide quantum dot materials.The film formation in the lead sulfide quantum dot wet process was studied.The near-infrared photodetector was fabricated and the device performance was tested and optimized.The following results have been achieved:?1?The spin-filming properties of lead sulfide quantum dots in different solvent systems were investigated.The appropriate number of times of filtration and the number of purifications have an effect on the quality and film-forming properties of quantum dots.?2?Photoconductive detectors with lead sulfide quantum dot materials have been prepared,and their performance can be achieved 486mA/W,detectivity is2.67×10¹¹Jones.?3?The photodiode of lead sulfide quantum dot material is prepared,and the performance is 0.262 A/W,900nm infrared light external quantum efficiency reaches36.1%.But the leakage condition is severe under high voltage,which affects the use of the guiding device.?4?The optimization theory of lead sulfide quantum dot photodiodes was analyzed,and an optimization solution was proposed based on the previous leakage current problem.The investigation of the film cracking caused by the exchange of quantum dot film ligands and the solvent volatility,viscosity,polarity,cleaning method,etc.all have an effect on the film quality.The quality of the film can be improved by changing the solvent and adjusting the atmosphere in the spin-coating room.In this thesis,the preparation method of lead sulfide photodiode is studied,the preparation process is optimized,and the optimization method of quantum dot film quality is explored,which provides ideas for the research and industrialization of lead sulfide quantum dot photodetectors.