The Influence Of Electrolyte Additives On DSSC Revealed By Operando Raman Spectroscopy

Dye-sensitized solar cell（DSSC）is currently the only commercially available non-silicon-based solar cell that efficiently captures solar energy.Due to its advantages of high photoelectric conversion efficiency,low production cost and simple preparation method,it has shown great advantages in a wide range of commercial production.This thesis is based on the advantages of Raman spectroscopy with high spatial resolution and in-situ non-destructive detection.In-situ/operando Raman spectroscopy was used to study the effect of electrolyte additives on the interface properties of DSSC.A method to quickly evaluate the open-circuit voltage(V_oc)of the important performance index of DSSC using in-situ/operando Raman spectroscopy has been established.At the same time,the real-time dynamic monitoring of the main species on the micro interface of the DSSC under working conditions using the micro-Raman spectroscopy imaging technology is also realized.It provides a new strategy for online quality control of DSSC commercialization.In this thesis,two complete DSSCs were studied as follows:1.Study the performance of DSSC without electrolyte additivesFirstly,it is assembled into a complete effective DSSC,then it is collected in real-time by in-situ Raman:（1）The Raman spectra of DSSC were collected,and it was found that there was one more Raman band at 164 cm^-1 in the short-circuit conditions than in the open-circuit conditions.（2）The spatial distribution of polyiodide ion in DSSC at the interface was clarified.（3）I₃^-(observed at 109 cm^-1),N719(observed at 1543 cm^-1)and I₅^-(observed at164 cm^-1)were selected as the research objects.Operando Raman spectroscopy was used to detect the bias-dependent effects of several bands.The results show that when the applied bias reaches V_oc,the intensity of the band at 164 cm^-1 closes zero.（4）The stability and regeneration of I₃^-(obserced at 109 cm^-1),N719(observed at 1543 cm^-1)and I₅^-(observed at164 cm^-1)were studied.It is found that I₅^-always exists in the electrolyte under the short-circuit conditions.Under the open-circuit conditions,no obvious Raman signal of I₅^-was observed in the electrolyte.This band disappears when the biaz applied to DSSC reaches V_oc.When a bias less than V_oc is applied again,I₅^-can be regenerated.This work found that the disappearance of I₅^-was correlated with V_oc.It laid the foundation for the next chapter to study the influence of electrolyte additives on the performance of DSSC.2.The influence of electrolyte additive TBP on the performance of DSSCIn order to verify the important conclusion drawn in the previous part:the disappearance of I₅^-is related to V_oc.We added the additive 4-tert-butylpyridine（TBP）to the Li I/I₂ electrolyte to increase the V_oc of DSSC.Then verify and analyze whether the disappearance of I₅^-is related to V_oc.The operando Raman acquisition was performed on the assembled effective DSSC（In this experiment,the wavelength of Raman excitation light is532 nm）:（1）Operando Raman acquisition of DSSC with TBP under short-circuit and open-circuit conditions,the results show that there is still one more band at 164 cm^-1 in the short-circuit conditions than in the open-circuit conditions.（2）The same method as the first part is used to study the bias dependence of Raman spectra of DSSC.The intensity and displacement of the Raman band of I₃^-(observed at 111 cm^-1),N719(observed at 1540 cm^-1)and I₅^-(observed at 164 cm^-1)with bias are discussed.It is found that the band at 164 cm^-1disappears when the applied bias reaches V_oc,which verifies the conclusion of the first part.The disappearance of I₅^-is related to V_oc,which is the signature band of DSSC’s normal operation.