| Since the unique properties of graphene are confirmed in 2004,the research on the preparation and properties of graphene-like two-dimensional layered materials has developed rapidly.Generally,two-dimensional layered materials can be delaminated into their nanosheets,these nanosheets exhibit tunable optical,electronic,catalytic and electrochemical properties,and they are important units for the development of high-performance optoelectronic devices and show broad application prospect.Single-element two-dimensional layered materials such as black phosphorus and borophene,etc.are a special type of two-dimensional layered materials,their preparation and the optoelectronic property will provide new basic research field and develop novel optoelectronic materials.Theoretical calculation results show that borophene has higher strength,better flexibility and conductivity than graphene,and it is expected to show great application potential in the fields of energy,sensing and catalysis.However,boron has a polyhedral crystal structure due to its bond-forming ability and richness compared to carbon,which tends to form a substance with a complex polyhedral structure.As a result,there has been no large-scale liquid phase preparation of borophene and their quantum dots up to now,severely limiting the large-scale application of borophene materials.In this thesis,bulk boron is used as the precursor and a liquid-phase ultrasonic thinning technology is employed to prepare borophene quantum dots(BQDs)with uniform size and good dispersion.BQDs/Ti3C2Tx composite film electrodes with different BQDs contents are prepared by assemblying Ti3C2Tx nanosheets with BQDs as pillaring agents.The modification of BQDs significantly improves the rate performance of the composite electrode materials and the energy density of assembled devices.At the same time,the prepared BQDs are introduced as interface modification materials between the functional layers of the perovskite solar cell to form a gradient energy level by passivating the interface defects,which improves the photoelectric conversion efficiency of the perovskite solar cell.The thesis is divided into five chapters.The first chapter is the summary of the related research,it mainly introduces the structure and properties of bulk boron and borophene,as well as the research progress of two-dimensional material quantum dots,and puts forward the significance,purpose and research content of this research.Chapters 2 to 4 are the experimental parts,mainly including the preparation and properties of BQDs,the preparation of BQDs/Ti3C2Tx composite film electrodes and the assembly of all solid-state flexible symmetric BQDs/Ti3C2Tx composite film symmetric capacitors,and the study on the preparation and properties of inorganic perovskite solar cell modified by BQDs;Chapter 5 is a summary of the full text.The main research contents are as follows:(1)Bulk boron powder is treated with liquid phase ultrasonic treatment in a mixed medium of NMP and NBA,and a new method for preparing BQDs with a uniform size and a size of about 4 nm has been developed.By studying the effect of ultrasonic treatment time on the morphology and size of the prepared BQDs,the best experimental conditions for preparing BQDs with uniform size and distribution will be determined.The relationship between the size and the band gap of BQDs will be calculated by density functional theory,and the band gap changes with the size of the BQDs will be studied.At the same time,the optical properties of the prepared BQDs will be characterized,and their blue fluorescence and good optical stability will be studied.Also the electrochemical properties of the prepared BQDs will be characterized,and the rate performance and electrochemical reversibility of the BQDs as electrode materials will be discussed.(2)BQDs/Ti3C2Tx composite film electrodes with different BQDs contents are prepared with the delaminated Ti3C2Tx nanosheets and the prepared BQDs with uniform size and good dispersion as pillaring agent.The morphology,structure and electrochemical properties of the BQDs/Ti3C2Tx composite film electrodes with different BQDs contents are systematically characterized,and the assembly regularity of BQDs uniformly loaded on Ti3C2Tx nanosheets will be revealed,and the optimal composite content of BQDs in the composite film will be discovered.The electrochemical properties of B-10 composite film electrode prepared with 10%BQDs content is characterized in 6 M H2SO4 electrolyte.When the current density is 1 A/g,the mass specific capacitance can reach 524 F/g,and it has a smaller the charge transfer resistance and the internal resistance of the solution.Using B-10 composite film electrode to assemble all solid-state flexible symmetrical capacitors,the electrochemical performance,mechanical performance,energy density and power density of the assembled devices will be systematically investigated,and improving the regularity properties of BQDs pillared BQDs/Ti3C2Tx composite electrode wiil be explained.The B-10 composite film electrode assembly device has good rate performance,the capacitance retention rate is 75%when the current density is increased from 1.25 mA/cm2 to 5 mA/cm2,and the capacitance retention rate is 93%when the scanning speed is 100 mV/s after 5000 cycles.The assembled device has good energy density,its volume energy density can reach 40.4 Wh/L when the power density is 416 W/L.Even when the power density reaches 1863 W/L,the volume energy density is still as high as 30.5 Wh/L.In addition,the assembled device also shows good mechanical properties,and the capacitance of the device was not significantly attenuated after different bending angles.The introduction of BQDs pillaring agent into Ti3C2Tx assemblyed film electrode material realizes the optimized balance between the specific capacity and flexibility of the prepared electrode material,and it will provide a new idea for developing high energy density flexible film supercapacitors.(3)The prepared BQDs is used to modify TiO2 electron transport layer of the perovskite battery to assemble the CsPbI2Br inorganic perovskite solar cell.By studying the changes in the strong electronic interaction between the BQDs modified perovskite layer and the TiO2 layer,it is revealed that the BQDs modified TiO2 film layer has a change in the top position of the valence band compared to the unmodified TiO2 film layer,making it more compatible with the perovskite energy level,and facilitating the transfer of photogenerated electrons from the perovskite layer to the TiO2 layer.At the same time,the open circuit voltage,short-circuit current and fill factor changes caused by BQDs modified CsPbI2Br solar cells are studied,and the optimal modification concentration of BQDs is selected,and the photoelectric conversion efficiency of the modified material assembled devices is investigated.On the basis of systematic research and characterization,the regulary that BQDs are used to interface modification of the perovskite solar cell to reduce the defect density at the interface and passivation of the electron transport layer and the perovskite layer will be explained,and the formation of gradient energy between the electron transport layer and the perovskite layer will be revealed.It is a effective way to improve the efficiency of electron transmission and the photoelectric performance of CsPbI2Br solar cells.The research will provide new ideas for realizing efficient and stable all-inorganic perovskite solar cells. |
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