Theoretical Study On Molecules Of Organic Dye Sensitizer Based On Phenothiazine ? Bridge

The dye-sensitized solar cell?DSSC?has attracted enormous attention due to some advantages such as simple fabrication,low production costs and high performance.Metal-free organic dyes,as one of the key components of DSSCs,play a pivotal role in light harvesting and electron injection.Among the various species of organic dyes,10H-phenothiazine-based dyes hold a large proportion due to its easily tunable structure,strong donor character and the unique non-planar butterfly conformation.Some 10H-phenothiazine-based dyes show high photovoltaic performance,even better than the commercial ruthenium complex?N719?.As we know,with the progress in density functional theory?DFT?,quantum chemistry calculation based on DFT has been a routine method to study the properties of sensitizers and guide molecular design.From a theoretical point of view,some efforts were made to investigate the electronic properties of candidates beforehand,which would be an efficient approach.Herein,based on quantum chemistry theory and method,we explore the effect of different structural components on the performance of 10H-phenothiazine-based dyes,aiming to establish the structure-performance relationship at a microscopic level.Our work mainly includes three parts as follows:First,we mainly describe the development process and research status of pure organic dye sensitizers,the basic structure,principles and characterization parameters of DSSC,some theories and research methods related to computational chemistry.Second,phenothiazine-based dyes with different donors or different substituent on N-10 position were comprehensive investigated by theoretical calculation.The molecular geometries of all dyes optimized at B3LYP/6-311G?d?.Some key parameters,such as dipole moment,energy gap,absorption spectra,the electrostatic potential of the dye molecule,dye regeneration and charge recombination of dyes were comprehensive studied using DFT and TD-DFT methods.The relationship between the dye molecular structure and performance from different aspects were investigated and discussed.Third,six new phenothiazine-based dyes with carbazolphenylene donor grafted to the phenothiazine?-bridge via ortho-,meta-,and para-position,together with alkylphenly and hexoxyphenyl on N-10 position were comprehensive investigated by theoretical calculation.Some key parameters,such as dipole moment,energy gap,absorption spectra,the electrostatic potential,dye regeneration and charge recombination also were comprehensive studied using DFT and TD-DFT methods.To deeply investigate interaction of dyes with the semiconductor surface,the adsorption structure of dye adsorbed on Ti O₂ was simulated using DFT.The adsorption mode,the distribution of the electron cloud,bond distances,the energy level and the state density of dye/Ti O₂was analyzed.