The Optimization,coplanar And Three-dimensional Modulation Of Triarylamine Dyes

The lack of conventional energy has become a stumbling block in the sustainment of the social and economic development.It is urgent to look for a new-style and environment friendly energy,while solar energy is what we need.Dye-sensitized solar cells(DSSCs)are a new type of solar cells which convert light to electricity by means of harvesting the solar irradiation by the sensitizer.DSSCs have drawn much global attention in scientific research and practical applications for their lower cost,much more simple preparation and higher conversion efficiency.The sensitizer,which was contained in the DSSCs,has a key role in determining solar-cell performance.Compared with rare and expensive ruthenium complex dyes,it is a wise decision to design low-cost and metal-free organic dyes which were easy to be modified.Triarylamine dye based DSSCs has provided a highly platform for metal-free organic dyes owing to their prominent electron donating ability.In this paper,two new types of triarylamine dyes were designed.Then we did theoretical calculations on their energy levels.Finally,a series of characterization was done with the DSSCs based on these dyes.Through the analysis of data,what we adjusted with the triphenylamine moieties turned out reasonable.On one hand,we took the reality that conventional triarylamine moieties are not planar into consideration.A new triarylamine dye characterized by planar reconstruction was obtained by rational design,which could significantly improve the conjugate degrees between three phenyl groups and center N atom.As a result,the electron donating ability of the triphenylamine unit was improved.However,this modification would contribute to the loss of its inborn spiral structure,which was a disadvantage to resisting dye aggregation.Based on this consideration,we designed and synthesized a new type of sensitizer which was marked by its three-dimensional coplanar structure.We selected a conventional triphenylamine sensitizer TTR1 from our previous work as the reference dye to make an evaluation on different photovoltaic parameters.The device based on NUIST1 gets a 21.1%higher energy conversion efficiency compared with the TTR1-based device fabricated under the same conditions.Moreover,it was proven by the UV-vis spectroscopic analysis that the novel 3D triphenylamine unit was outstanding for it higher electron donating ability.Last but not least,its 3D structure could help resist dark current and restrain charge recombination,as evidenced by dark current and electrochemical impedance spectroscopic(EIS)studies.All the results mentioned above demonstrated the rationality of reconstructing coplanar triphenylamine units.On the other hand,in order to improve the electron donating ability of the dye,a novel dye(CPAR1),which was characterized by introducing heterocyclic groups into triarylamine units and added a new anchoring group(rhodanine-3-acetic acid),was designed and synthesized.Then we did analysis on the DSSCs based on CPAR1,whose overall power conversion efficiency(PCE)was 5.9%,then it was found that photovoltaic performance of the DSSCs can be enhanced by introducing suitable heterocyclic groups to triarylamine moieties,partly due to the reason that heterocyctlic groups would partly delocalize the positive charge after photooxdation.So it could be inferred that using suitable heterocyctlic groups to reconstruct triarylamine moieties could indeed boost up their electron donating ability.Moreover,we utilize rhodanine-3-acetic acid as the electron acceptor,which could demonstrate that the attempt to improve anchoring group was vital to the enhancement of the DSSCs.