Theoretical Study On Intramolecular Charge Transfer Of Two Novel Dyes

With the development of human society, the demand of energy sources isincreasing in more recent decades.At the same time,the traditional natural energy isdecreasing,such as natural gas,petroleum and coal.So searching for new source ofenergy is the focus of attention of human being at present.And the solar cells haveattracted considerable attention by the abundant resources andnon-pollution.Therefore,people have paid attention to the development andutilization of sola cell.Dye-sensitized solar cells (DSSCs) have attracted considerableattention of people with its low lost,simple processing technology and higherstability.It has vast prospects.Dye-sensitized is the key part of DSSCs, which absorbs photoelectronscoming from sunlight and transfers the photoelectrons to conduction band (CB) ofTiO2.Dye molecules can be excited and produce electron-hole pairs which separateat the interface，and flow in the closed loop in the opposite direction, generatingelectric current and achieving the photoelectric conversion.So the photoelectricconversion is influenced by the property of dye sensitizer.In this paper,we studied two novel dyes as a research object.They were dyePCDTBT which had carbazole as electron donor and thienyl-benzothiadiazole aselectron acceptor and dye silicon phthalocyanine that coordinates twoanthracene-9-carboxylate groups in the form of trans axial ligands which hasanthracene-9-carboxylate as electron donor and silicon phthalocyanine as electronacceptor.We used the quantum chemistry methods in the theoreticalstudy.Researchde the property of their excited state with parameter ofTD-DFT B3LYP6-31G（d） of Time Dependent-Density Functional Theory.Andthen listde their HOMO and LUMO.We got the results that the first one had twomain visible bands at614.90nm and395.00nm were mainly attributed to theelectronic transition from HOMOâ†'LUMO and HOMOâ†'LUMO+1and the otherone had two main visible bands at659.92nm and653.34nm were mainly attributed to the electronic transition from HOMO-2â†'LUMO and HOMO-2â†'LUMO+1.3Dcube representations including transition density and charge difference densityvisualized the character of intramolecular charge transfer of two novel dyes.Furthermore,we use2D cube representations to analysis the coherence ofelectron-hole.