| Forests and green plants provide energy for the entire biosphere through photosynthesis.Dye-sensitized solar cells(DSSC)mimic partial mechanism of photosynthesis and improve the solar energy utilization of the cells by sensitizing semiconductor with pigments.Compared with the common solid battery,DSSC features great flexibility and is able to utilize the ambient light in addition to the direct light.Therefore,the prospect of its application on portable forest engineering equipment is broad.Forest resources provide a wide range of natural pigments such as anthocyanins and chlorophyll.Compared with industrial dyes,natural dyes are non-toxic and pollution-free,but their effective use of sunlight depends on the complex energy and mass transfer structure in plant cells.Research on how to modify the structure of natural pigments to adapt the working environment of DSSC is of great significance for improving the comprehensive utilization of forest resources.Compared with other natural pigments,pyranoanthocyanidins have unique stability and good application prospects in natural dye-sensitized solar cells.In this paper,the following work has been done to study the photovoltaic performance of pyranoanthocyanidins(1)In this paper,the structure-property relationship of the reported pyranoanthocyanidin dye sensitizers has been theoretically studied through computational chemistry.It is found that the overall structure of pyranoanthocyanidin is of planar configuration.Introducing strong electron donors increases the planarity of the molecule and enhances the electron conjugation,which leads to bathochromic shift of the light absorption sprectrum.The adsoption of dyes with catechol functioning as anchor group is more stable than that with carboxyl group,and the electron coupling between the dye and the TiO2 photoanode is stronger for catechol,which accelerates the electron injection process.Mono-hydroxyl AF3(dye d)can also adsorb on the surface of TiO2 and inject electrons into the TiO2 semiconductor.Pyranoanthocyanidin dyes can be regenerated by iodide anions,but there are also unfavorable charge recombination phenomena.The more serious charge recombination and smaller vertical dipole moment may cause the gap between the performance of pyranoanthocyanidin-based dye-sensitized solar cell and the DSSC based on D-?-A organic dyes.(2)As related experiments and theoretical calculations show that AF3 can adsorb on the surface of TiO2 via single hydroxyl group at the C-7 position,the B ring E ring at both ends of the molecular structure can function as electron-donating groups.Therefore two pyranoanthocyanidins with double-donor structures were designed by introducing another dimethylamino group and two methoxy groups to the phenyl group of AF3.The two new pyranoanthocyanidins were synthesized by organic methods,and the structure and purity of the dyes were determined by means of NMR and LC-MS spectrometry.(3)The synthesized pyranoanthocyanidins,AF3-1 and AF3-2,were successfully applied to dye-sensitized solar cells.The photophysical and electrochemical properties of the dyes and photoelectric conversion efficiency of dye-sensitized cells were tested and characterized.The aggregation of dyes on the anode semiconductor surface is more serious for AF3-2,resulting in its lower photoelectric conversion efficiency.AF3-1 has an energy conversion efficiency of 1.79%due to the red shift of the absorption spectrum,lower anode/electrolyte interface impedance and higher dye loading amount.Compared with the prototype dye,AF3,the open circuit voltage of DSSC is increased from 332 mV to 480 mV,but the short-circuit current density is reduced due to the influence of dye aggregation,with photoelectric conversion efficiency turning out to remain the same level. |
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