Research On PbS Quantum Dot Composite Silicon Nanowires Near-infrared Detector

The silicon based photodetector is limited by its own band gap and cannot respond to the wave band after 1100 nm.Pb S quantum dot composite one-dimensional silicon nanowires can effectively expand the response wavelength of silicon based photodetectors,and is an effective way to obtain in situ integrated wide spectral silicon photodetectors.At present,the preparation methods of Pb S quantum dots mostly use solvothermal and ligand exchange methods based on organic metal compounds.The Pb S quantum dots prepared by this method exhibit monodisperse characteristics,that is,narrow band light absorption and response characteristics,making it difficult to achieve wide band response.In addition,there are a large number of organic ligand residues on the surface of quantum dots,which are easily affected by the environment,easily oxidized,lose activity,and have poor stability.This article uses the successive ionic layer adsorption and reaction method to successfully prepare polydisperse Pb S quantum dot films on the surface of silicon nanowires.The material properties are characterized,and a prototype device of Pb S quantum dot/silicon nanowires core-shell structure is prepared.The photoelectric characteristics of the device are tested,and the photoelectric response mechanism is studied and discussed.The main results and conclusions obtained are as follows:（1）The nanoscale growth of Pb S quantum dots in silicon nanowires microstructures was achieved:The successive ionic layer adsorption and reaction method was used to successfully prepare Pb S quantum dot thin films in silicon nanowires.The effects of experimental parameters such as cycle times,deposition time,and annealing temperature on the Pb S quantum dot thin films were studied,and a fully coated and uniformly thick Pb S quantum dot/silicon nanowires core-shell structure was obtained.（2）The main components of Pb S quantum dot films were characterized,and the absorption spectra of Pb S quantum dot/silicon nanowires samples were obtained:XRD,XPS,and EDS energy spectrum analysis were used to characterize the phase information,element content,and element types of Pb S quantum dots,and to explore the issues of quantum dot crystallinity,element existence forms,and element distribution regions in Pb S quantum dot/silicon nanowires with different parameters;The core-shell structure of Pb S quantum dots/silicon nanowires was observed using FESEM and TEM,and the microstructure,particle size,and distribution of Pb S quantum dots were clearly observed;The absorption rate of Pb S quantum dots/silicon nanowires was tested using a spectrophotometer,and the absorption spectra in the visible near-infrared band were obtained.（3）The Pb S quantum dots/silicon nanowires core-shell prototype device was prepared,and the photoelectric response characteristics were optimized:A test platform was built to test the photoelectric characteristics of the Pb S quantum dot/silicon nanowires core-shell photodetector in the range of 400-2200 nm.The detection rates at 980 nm,1200 nm,1650 nm and 2200 nm are2.18×10¹⁰ Jones,2.23×10⁹ Jones,1.75×10⁸ Jones and 2.23×10⁷ Jones,respectively.The responsivity at 1200 nm,1650 nm and 2200 nm reached 799.1μA/W,187.5μA/W and 10.517μA/W,respectively.The vacuum annealing technique is used to improve the crystallinity of the quantum dots effectively,so as to improve the photoelectric response characteristics of the devices.The experimental results show that the device has the best performance when the annealing temperature is 150°C.（4）We studied the photoelectric response mechanism of Pb S quantum dot polydispersions and explored the stability mechanism different from colloidal quantum dot devices:Through characterization of the prepared Pb S quantum dots,it was found that the particle size distribution of Pb S quantum dots prepared by the successive ionic layer adsorption and reaction method was between 3-15 nm,and the number of cyclic deposition times had a significant impact on the particle size of the quantum dots.Quantum dots with different particle sizes have different light absorption peaks.Under the synergistic effect of quantum dots with different particle sizes,the polydisperse Pb S quantum dots/silicon nanowires array core-shell structure prepared in this paper has wide spectral（400-2500 nm）absorption characteristics.Pb S quantum dots provide most photo generated carriers in the near-infrared band,breaking the response limit of silicon-based photodetectors and achieving broadband photoelectric response（400-2200 nm）.In addition,the response characteristics of devices placed for a long time in the atmospheric environment show no attenuation,indicating that the Pb S quantum dot/silicon nanowires array core-shell heterojunction photodetector prepared in this paper has excellent environmental and time stability.The performance of the Pb S quantum dot/silicon nanowires array core-shell heterojunction photodetector prepared in this article is compared to the results reported in literature,which has a wider spectral absorption range,better stability,and excellent photoelectric response.The device can still optimize its structure to improve device performance.For example,designing new device structures to increase response current;Introducing a tunneling layer to reduce dark current;Alternatively,the above methods can be used for joint regulation to achieve a higher light to dark current ratio.The research work of this article provides new ideas for the development of broadband detectors.