Study On Preparation And Optoelectronic Properties Of New Bi₂O₂S?Se? Low-Dimensional Materials

As the precision of integrated circuits continues to increase,the development of devices also tends to become more compact,advanced,high-density,fast-transport,high-capacity,and intelligently controlled,resulting in increasingly stringent material performance and size requirements.Low-dimensional materials are widely used in optoelectronics,biomedicine,and energy because of their unique thermal,mechanical,magnetic,optical,and electrical properties.Compared with other materials,the new layered bismuth oxysulfide materials are seized of excellent semiconductor characteristics of high mobility,stable environment as well as bulk preparation,making them unique in constructing new optoele ctronic devices.In this paper,Bi₂O₂S and Bi₂O₂Se low-dimensional materials were prepared by a mild one-step hydrothermal method without adding any molten metal and reducing agent.The effects of preparation parameters on the phase structure and morphology of the materials were investigated and the performance of photodetectors based on Bi₂O₂S/Bi₂O₂Se thin films was studied.Finally,The breakthrough application of Bi₂O₂S as a negative electrode in supercapacitors was achieved.The main research contents are as follows.The synthesis of the Bi₂O₂S?Bi₂O₂Se nanosheets by one-step hydrothermal method.When using ammonium citrate as a source,the best parameters are that the NaOH concentration is 0.95 mol/L,the ratio of alcohol to water is 1:1,the reaction temperature was 200°C and the time is 24 h.The average size of the single crystal Bi₂O₂S nanosheets with a regular square structure was 1.0?m,and the thinnest thickness of the single sheet was 4.6 nm.The Bi₂O₂Se low-dimensional material is prepared by one-step hydrothermal method without adding any reducing agent.The study shows that the best parameters:the KOH concentration was 3.5 mol/L,the reaction temperature was 230°C,and the time was 24 h.The obtained Bi₂O₂Se low-dimensional material menifests the best phase with single crystal structure and good crystallinity,and the thinnest thickness of the single nanosheet was 4.7 nm.Compared with bismuth nitrate as the source of Bi,it is found that the intercalation of citrate ions in the interlayer restrict s the growth of the material along the c-axis,so that the Bi₂O₂S material grows into nanosheet along two directions.The Bi₂O₂S and Bi₂O₂Se thin films are prepared by thermal spraying method.Photodetectors based on these two films are prepared.The optoelectronic performance of Bi₂O₂S-based photodetectors is the best under 532 nm illumination;Bi₂O₂Se-based photodetectors have the best overall optoelectronic performance at 785 nm illumination,both of which exhibit excellent optoelectronic performance.The response time of the Bi₂O₂Se-based detector irradiated at 532 nm is 81.9 ms,the highest responsivity is 0.059 A/W,the highest detectivity is 6.77×10⁹ Jones;when the light is irradiated at 785 nm,the response time is 78.85 ms,the highest responsivity is 75.14 A/W,and the highes t detectivity is 3.95×10¹² Jones,which shows better photoelectric performance.The electrochemical performance of Bi₂O₂S as an electrode material in a three-electrode system is studied.It is found that in the three-electrode system the Bi₂O₂S electrode has a higher specific capacitance(902.8 Fg^-1)while maintaining better rate performance in the 1 M KOH solution.After the incorporation of graphene,the Bi₂O₂S/RGO electrode not only has a higher specific capacitance(826.27 Fg^-1),but also has a significantly improved cycle stability.