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In Situ Raman Study Of Electrolyte/Dye Interactions In Dye-sensitized Solar Cells

Posted on:2021-05-20Degree:MasterType:Thesis
Country:ChinaCandidate:Y T YeFull Text:PDF
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Dye-sensitized solar cells?DSSC?have attracted much attention due to their low cost and environmentally friendly behavior.However,there is still a gap between DSSC's theoretical efficiency and actual efficiency.Historically,researchers have mainly improved the overall performance of cells by continuously improving the interface thickness and interface structure.It can be seen that the"interface"plays an important role in the overall performance of the DSSC.However,the various analysis methods currently used for DSSC interface characterization have failed to achieve in situ detection of DSSC under actual working conditions.Therefore,this article is devoted to establishing a new and effective DSSC in situ characterization technology to study the evolution process of the DSSC interface under working conditions,so as to provide theoretical basis and technical support for improving the performance of DSSC.Resonance Raman scattering?RRS?,as a high-sensitivity vibration spectrum,can provide fingerprint spectra,and under non-destructive conditions,the specific spectral band of the sample can produce a large resonance enhancement.In this paper,the in situ study of DSSC was carried out by resonance Raman technology.The interaction between dye and electrolyte was analyzed by in situ Raman spectroscopy,and the relationship between cell efficiency and resonance Raman spectrum was discussed.This article also discusses the following research contents:1.In situ study of the evolution of electrolytes in non-dye-sensitized solar cells by Raman spectroscopyA highly ordered TiO2 nanotube array?TNA?was prepared by anodization,and non-dye-sensitized solar cells were assembled using KI/I2 as the electrolyte.By studying the real-time Raman spectrum of the solar cell under working condition with 532 nm laser,we identified the effect of carrier separation at TNA interface on I3-and I5-regeneration at molecular scale.In addition,by adjusting the laser intensity to monitor the formation and conversion of I5-in solar cells,we found:?1?When collecting the in situ Raman spectrum of the cell and monitoring the current-time?I-T?curve of the cell at the same time,we proved that the cell had a significant photocurrent response to the excitation light at 532nm.?2?Selecting the vibration band(located at167 cm-1)with strong response to 532 nm excitation light as the research object,its displacement and intensity during loading were discussed.Our study found that with the increase of the bias,the band intensity gradually increased,and the band position also moved to a lower wave number.When the applied bias came close to the open circuit voltage(Voc)of the cell,the cell could not work spontaneously,and this band disappeared.Also,we found that the I3-band(at 110 cm-1)had a major transition and intensity change,while the band which attributed to titanium dioxide(located at 146 cm-1)basically remained unchanged,indicating that I3-and I5-can be regenerated at voltage lower than the Voc.?3?By adjusting the laser power,the dependence on the laser power and the laser band position at 167 cm-1,which is the band intensity,was studied.The morphology and crystal structure of TNA and photoanode was characterized by scanning the electron microscope and x-ray diffraction.This section of work proposed a technique for real-time monitoring of the the solar cell interface under the working conditions from the molecular scale,and determined the origin of the band at 167cm-1 and the effect of regeneration over the cell performance,providing the research foundation of the next chapter's study on in situ study of DSSC.2.In situ study of the interaction between electrolyte and dye in dye-sensitized solar cells using Raman spectroscopyBased on the research results and on the basis of the previous section,we further upgraded the solar cell structure.We added a dye sensitizer?dye N719?to the cell,and used Raman spectroscopy to conduct in situ research on the complete DSSC.Except for the dye,this section of the photoanode is the same as the first section.In other words,anatase TNA is used for photoanode,N719 is used for dye,and KI/I2 is used for electrolyte for further study.Subsequently,the in situ study of the interaction process between the electrolyte and the dye precipitated in the interface of the complete DSSC by Raman spectroscopy included:?1?The in situ Raman spectroscopy of the previous section is still used to study DSSC in working condition.The band of N719 dye at 1535 cm-1 is the main research for analysis and discussion.several strong vibration band of N719 dye.The study showed that the C=C stretching vibrations of the dipyridine in the dye molecule are very sensitive to the loading process.?2?The study found that the band intensity at 170 cm-1decreases with the increase of the applied bias.When the bias increases close to the Voc?0.6 V?,the band disappears;when the applied bias is less than the Voc,the band appears again at 170 cm-1.?3?When performing DSSC laser power control test,we found that the C=C stretching vibration band of N719 dye show a significant dependence on laser power.That is,the intensity of the band increases with laser power,and as the laser power decreases,the intensity of the band also decreases.This reversible laser power dependence indicates that the N719 dye in DSSC is regenerable under working conditions?electrodes do not have this reversible dependence?.?4?DSSC in situ Raman spectroscopy imaging proves the repeatability and reproducibility of Raman detection.3.Effect of high-efficiency electrolyte in DSSC revealed by in situ Raman spectroscopyIn the previous section,the DSSC with electrolyte composition of KI/I2 was used for in situ Raman studies.In this section,by changing the electrolyte composition,the DSSC containing three electrolyte compositions:KI/I2?Et36 and Et23,was studied,and the relationship between cell performance and Raman spectrum was discussed,too.The results showed that the photoelectric conversion efficiency of the cell has a certain dependence on the position of the Raman band of the DSSC's N719 dye.Specifically,as the conversion efficiency increases,the C=C vibration of N719 moves to smaller wave numbers.
Keywords/Search Tags:Resonance Raman, Raman spectroscopy, Raman scattering, Titanium dioxide, Dye-sensitized solar cell
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