Theoretical Study On The Construction Of High-performance Sensitizers In DSSC

Dye-sensitized solar cell is a photosensitive devices that can efficiently capture solar energy in the new period.Due to its high photoelectric conversion efficiency,good thermal stability,low production cost and simple preparation scheme,the DSSC possesses huge advantages in large-scale industrial production,which is widely used in aerospace,military,communications and other fields.DSSC is made up by transparent conductive optical glass,semiconductor photoanode,sensitizer,electrolyte and counter electrode.Among them,the sensitizer can availably capture sunlight,collect photons,separate excition and generate electrons injected into semiconductor,these processes play a significant role in regulating the performance of DSSC.Therefore,it is a key point to design and synthesis the high performance sensitizers.Based on the density functional theory,in current content,insighting into the theoretical investigation of the strategy that how to construct a high performance Ru（II）dyes and a series of organic dye,and providing some directions for future application in DSSC.In addition to investigating the properties of isolated dyes,the analysis of the density of states,the charge density difference,and the interface electronic injection are used to further explore the interface interaction between the dye and semiconductor.This thesis is divided into five chapters.The first chapter is the preface,summarizing the brief development history of solar cells and the milestone events in dyesensitized solar cell.The basic structure and working principle of dye-sensitized solar cell are concisely introduced.And the existing design and synthesis of high-performance sensitizers agent program,and explain the meaning of this thesis.The second chapter is the description of the theoretical calculation method used in this paper,including the basic theory of quantum mechanics and the main computational methods of modern quantum chemical processing;additionally,we have carried out a detailed overview of the means that can be used in the research process.These include the introduction of geometric structure,electronic structure,intramolecular electronic transport property,light trapping and utilization,dyeelectrolyte interaction,and dye-Ti O2 complex system.In the DSSC theoretical research,researchers often use these test techniques and evaluation programs,through the study and discussion of the relevant results,we can in-depth understanding and reveal how the nature of the sensitizer configuration differences affect the DSSC performance.Hope that through the summary of this chapter,we can provide strong technical support for the follow-up work.The third chapter and the fourth chapter are to introduce the specific content ofhigh-performance sensitizer program and related character means.The related research contents are as follows: 1.In this chapter,we select a representative ruthenium metal sensitizer as prototype dye.The density functional theory（DFT）and time-dependent density functional theory（TD-DFT）method are applied to investigate the effect of interfacial structure between dye and semiconductors on the performance of DSSC.This work is carried out based on the previous work of our group.In addition to exploring the molecular structure,electronic structure and optical properties of the isolated dye,the work also investigates the effect of the p H value of the solution and the combined system by the dye and semiconductor on DSSC.A highlight of this work is that we first proposed the calculation method of the maximum short-circuit current in the theoretical calculation work.In the calculation,we made a series of pushes to the expression of the photon flux （φ（λ））,finally,the relationship between the maximum photo current andφ（λ） is obtained.Due to the quantity of electricity passing through the cross-sectional rea of the conductor per unit area per unit time is equal to the maximum hort-circuit current(max J_sc^max),thus,it is possible to use this method to quantitatively easure the short-circuit current of the DSSC.The results of this work show that he alkaline solution environment is conducive to enhancing the efficiency of the SSC.In addition,the work confirms that the interfacial structure between the ye and the semiconductor can greatly affect the performance of the DSSC.2.With the foreshadowing of the previous work,we naturally want to test methods, nalytical methods used in other types of sensitizers,in addition to verify the ationality of our analysis methods,but also to put forward some comprehensive nd universal conclusions on the key issue that how to construct high-performance ensitizes.In DSSC field,due to the lager extinction coefficient,great hotochemical and photophysical properties,low-cost and free from resource onstraints,the organic sensitizers have attracted a wide range of attention.In eneral,the excellent organic sensitizers usually present a push-pull configuration, hich is composed by an electron donor group（D）,a conjugated linker（π）,and n electron acceptor group（A）,with the acceptor part anchored on the emiconductor surface.This structure is favor of the intramolecular charge ransfer from the donor moiety to the acceptor unit through the p-spacer,and hotoexcited electrons inject into the semiconductor,as well as the regeneration of xidized dyes.The three parts play an independent and positive role.Among them, he electron donor part plays a key role in regulating the absorption spectra and olecular energy level;π bridge part processesabsorbance range and ntramolecular electron transport process,while the electron acceptor part of the ntramolecular electron injection process.Therefore,the independent modification f the three parts can provide favorable conditions for us to better explore the ependence between the structure of the sensitizer and the photoelectric onversion performance.With the purpose of further enhancing the photoelectric onversion efficiency of sensitizers,in this chapter,we from the theoretical point f view,through the exploration and summary of four small work,a omprehensive introduction to how to build high-performance organic sensitizers nd the need in the construction process attention questions.It is hoped that the ummary of this chapter’s work can provide favorable technical support for the mooth development of our follow-up work.The fifth chapter includes a summary of the research results achieved at the current stage and a brief introduction of an under review work,as well as the development plan for the future work.