Synthesis And Performance Studies Of Novel Indoline Dyes Regulated By Planarization

Dye-sensitized solar cell（DSSC）have received widespread attention as a potential alternative for conventional silicon-based solar cell over the past two decades due to reasonable photoelectric conversion efficiencies.With the in-depth development of organic dyes,targeted and selective energy regulation has become an increasingly important issue.In this paper,four indoline sensitizers based on D-π-A-π-A structure with identical donor and acceptor units are designed and synthesized,and their molecular planarity is regulated by the introduction of various side chains into donor bridges.The photophysical,electrochemical,and photovoltaic properties of the four dyes are studied in detail.In chapter 1,the development of DSSCs,as well as the characteristics,types and classification of dye sensitizers are briefly introduced.The main issue of the development of organic dyes are summarized,based on which,the design ideas of this paper are introduced:targeted and selective energy regulation by molecular engineering.In chapter 2,with indoline as the electron donors,benzothiadiazole as auxiliary receptor,and benzoic acid as acceptor,a series of new sensitizers,CS-25,CS-26,CS-27 and CS-28 are designed and synthesized.The molecular planarities of these dyes are adjusted by introducing different side chains.The chemical structures of all the intermediates and target compounds are characterized by NMR spectroscopy.In chapter 3,the photophysical,electrochemical and photovoltaic properties of four novel dye sensitizers are studied,and the Gaussian 09 program is used to quantify the properties of the ground state and first excited state of four dyes.Along with the improvement of planarity at donor bridge,the HOMO levels of the dyes lift gradually,and more importantly,their LUMO levels remain around the same value.Besides,higher charge injection efficiency is obtained by the better molecular planarity,while too planar molecule may cause higher HOMO level,leading to poor dye regeneration efficiency.Furthermore,appropriate side chain also restrains the charge recombination to some extent,while too large side chain may give more chance for I₃^﹣to recombine with charge in conduction band.As a result,the best photovoltaic performance is obtained by CS-26.In chapter 4,the conclusions are presented.The results demonstrate that the regulation of planarity at donor bridge can not only targeted and selectively control the HOMO of the dye,but also finely adjust multiple interfacial charge transfer processes.The molecular planarity deserves to play an important role in the design of organic dye,providing a significant strategy for the further development of efficient sensitizer.