Synthesis And Properties Of Novel Indoline Sensitizer

Recently,dye-sensitized solar cells(DSSCs)have attracted great research interest as an emerging renewable photovoltaic device.Sensitizers play a key role in DSSCs,which participate in the capture of sunlight and electron transport,which directly determine the photovoltaic performance of cell devices.Pure organic dyes are favored due to their low cost,high structural flexibility,environmental friendliness,high molar extinction coefficient,and easy synthesis.Based on our previous studies,the improvement of molecular planarity in donor segment can not only broaden the spectral response range,but also optimize the interfacial charge transport processes.However,whether the planarity at other part of the dye molecule presents the same regulation effect is still unknown.Therefore,in this thesis,by applying the molecular planarization engineering in the donor-conjugated bridge part,the regulation effect of planarity on the properties of the sensitizers is investigated.In chapter 1,the research background and the development of DSSCs is introduced,as well as the working principle and parameters of cell devices.The molecular engineering of indoline-based sensitizing dyes is also reviewed in detail.The design ideas and research contents of this thesis are proposedIn chapter 2,two novel sensitizers,CS-73 and CS-74,are designed and synthesized,using indoline as the donor,thiophene as the ? bridge,and benzothiadiazole as the auxiliary acceptor.The planarity between the donor and the ? bridge of CS-74 is improved by the cyclization reaction.The chemical structures of the target compounds and all the intermediates are characterized by NMR spectroscopy.In chapter 3,the photophysics,electrochemistry,theoretical calculation,and photovoltaic properties of the two dyes are characterized and investigated in detail.It's found that the planarization at the donor-conjugated bridge chain can effectively narrow the band gap between HOMO and LUMO levels.Compared with CS-73,the absorption band of CS-74 is expanded,while the molar extinction coefficient is also increased,thus resulting in the enhancement of light-harvesting capability.Moreover,CS-74 also presents higher charge injection efficiency,with respect to CS-73.As a result,the DSSC device based on CS-74 obtains higher open-circuit voltage and short-circuit current density than that of CS-73,showing better power conversion efficiency.In chapter 4,the conclusions are presented.It is found that planar molecular engineering at the donor-conjugated bridge chain can narrow the energy band gap of the dye,expand the absorption spectrum of the dye,and improve the light-harvesting ability of the dye.In addition,planarized molecular engineering can also optimize the interfacial charge transfer process of the cell devices,further enhancing its photovoltaic performance.Molecular planarization is an effective regulation method,which provides a meaningful reference for the development and design of efficient organic sensitizing dyes in the future.