Improve Dye Performance By In Situ Embedding Phosphorus Or Boron Atoms Onto Boron Dipyrromethene(BODIPY) Framework

As one of the third-generation thin-film solar cells,the dye-sensitized solar cell(DSSC)has caused scientific research work and widespread concern because of its low cost,simple manufacturing process,high photoelectric conversion efficiency,and green pollution-free.In 1991,Gratzel reported the first DSSC with a photoelectric conversion efficiency of 7.1-7.9%.Since then,dye-sensitized solar cells have entered a new journey.With the progress of the times and the development of science and technology,this solar cell has achieved a photoelectric conversion efficiency of 15%so far.However,in the commercial field,due to the chemical stability problems,the performance of this photovoltaic device is expected to be further enhanced,so that it can accelerate the commercial process.Traditional DSSCs are composed of five parts,which are transparent optically conductive glass substrate,semiconductor as anode,dye sensitizer,electrolyte solution and counter electrode.As one of its core components,dye sensitizers have important implications for the performance changes of DSSC devices.Therefore,in order to obtain high-performance dye sensitizers,rational design and optimize dye molecules will be the key to improving the performance of DSSC.In this thesis,we take the dye monomer CB2((E)-2-cyano-3-(5,5-difluoro-8-(9-(4-methoxyphenyl)-9 H-carbazole-3-yl)-1,3,7,9-tetramethyl-10-pentyl-5 H-5λ4,6λ4-dipyrrolo[1,2-c:2’,1’-f][1,3,2]diazaborinin-2-yl)acrylic acid),which has been synthesized experimentally,as the research object,and embedding electron-rich phosphorus atoms(P)and electron-deficient boron atoms(B)on the π-spacer to enhance the performance of the dyes for the application of DSSC.The related research contents are as follows:1.In the first chapter,the background and development of solar cells and the third-generation solar cells represented by dye-sensitized solar cells are introduced in detail.The basic structure and working principle of dye-sensitized solar cells are also described in detail.The research content and significance of this thesis are also expounded.2.In the second and third chapter,the theoretical method and calculation details used in this thesis are described in detail.It mainly includes the basic theory of quantum mechanics and the simulation calculation method of modern quantum chemistry,as well as the process are studied in this thesis,for example,the introduction of the exploration process and analysis of the corresponding results of the geometric structure,electron absorption spectrum,light capture and utilization,intramolecular charge transfer rate and electron injection kinetics of the dye-TiO2 complex system.3.The fourth chapter,we made a detailed discussion of the research on theoretical design and research on electron-rich/deficient atom(P/B)to improve dye sensitizer performance.We designed a series of novel dye sensitizers by doping electron-rich P atoms and electron-deficient B atoms onto the π-spacer(BODIPY)of the prototype dye CB2 to construct electronic defects.Subsequently,we used density functional theory(DFT)and time-dependent density functional theory(TD-DFT)to carry out theoretical calculation simulations respectively.We analyzed the electronic absorption spectra of all dyes to determine the absorption spectra of the dye molecules after B or P atom doping,and further selected the target dye molecules with excellent solar absorption properties.On this basis,we used the parameters,such as light harvest efficiency(ηLHE(λ))and photo-generated short-circuit current density(JSC),to quantitatively evaluate the effect of the embedding position on improving the photoelectric conversion performance.Finally,we adopted Marcus charge transfer theory and semi-classical quantum dynamics simulation to study and explain the intramolecular charge transfer and electron injection of the dye-TiO2 complex system respectively.The results shown that the formation of electronic defects at the core of BODIPY is conducive to the improvement of dye performance.Embedding electron-rich P at the BODIPY axis(a,b sites)could not only lead to wide effective absorption coverage induced high short-circuit current density of 22.00 mA cm-2,but also promote charge separation of the parent dye and inherit the IET performance to the maximum extent.4.In the fifth chapter,it mainly introduces the work summary of this thesis,and the future prospects of this work.