| Polyoxometalate(POM)is a class of transition metal inorganic clusters with the highest oxidation state or mixed valence state.It is composed of d0 or d1 transition metals bridged by oxygen atoms.In recent years,POM shows favorable application prospects in DSSC,photocatalysis and photothermal therapy.With the adjustable energy band structure,remarkable visible light absorption performance and strong electron acceptability,it has received extensive attention as a medium or co-sensitizer in photoanode materials for DSSC.Referring to the combination of dye molecules and POM as cosensitizer in DSSC to improve the photoelectric conversion efficiency.In this dissertation,we introduce this concept into the all-iquid-state electrochemical cell to achieve effective photoelectric conversion.In addition,the mixed-valence POM exhibits excellent photothermal performance due to a new intervalence charge transfer(IVCT)band appears in the long wavelength region.Meanwhile,the reversible redox activity and the structure stability of mixed-valence POM will be suitable for redox related energy conversion processes,such as thermoelectric conversion.Mixed valence POM can utilize the combination of thermoelectric effect and photothermal effect,eventually achieves the photo-thermo-electric conversion.Basing on the above analysis,the main contents included in this dissertation are as follows:1.For currently developed 3rd generation solar cells,the fabrication techniques played a critical role on their performance.High efficiency and durability require meticulous and complicated control over the charge separation,recombination and transfer,as well as package technique in a solar cell system.The DSSC and perovskite solar cells(PSCs)in solid/liquid configuration are suffering low durability owing to leakage and corrosivity of liquid electrolytes.In view of this,we fabricate a simple cell structure.The hybrid inorganic-organic ionic semiconductor[Ni(Phen)3][V14O34Cl]Cl(Phen=1,10-phenanthroline)dissolves in ionic liquid solution as electrolyte,and different electrode materials are immersed in this solution to characterize the photoelectric response.Through optimizing electrode materials,cell configuration:carbon cloth ‖[Ni(Phen)3][V14O34Cl]Cl in ionic liquid ‖ Al foam yields an open-circuit voltage of ca.1.199 V and photocurrent density of 3.268 mA cm-2 upon illumination using AM 1.5(100 mW cm-2)at 80℃ with a fill factor of 42.48%and an efficiency of 1.665%.In addition,we analyze the electron transfer process of photoelectric conversion by the co-sensitization of metal-organic coordination cations and POM anions with the help of ultrafast spectroscopy characterization.2.A large fraction of energy,including solar energy,is dissipated into ambient atmosphere as low-grade waste heat.Efficient utilization of such energy is critical to address current energy crisis and global warming issue.We achieve the efficient NIRphotothermal,thermoelectric and thus photo-thermo-electric conversion of polyoxovanadate compound([Ni(phen)3][V14O34Cl]Cl,NiV14)in ionic liquid.The solution displays a NIR-photothermal efficiency of 16.04%and 23.43%at 808 and 1064 nm,respectively.Taking advantage of the synergetic thermodiffusive and thermogalvanic effects of various ions species in NiV14 solution,we achieve a thermal voltage of ca.0.45 V at ΔT=70 K generated by physical heating or NIR irradiation,indicating a large Seebeck coefficient of 6.38 mV K-1 and an optimized thermal power at 1.2 W m-2.Polyoxovanadate-ionic liquid system offers a new platform for efficiently utilizing not only low-grade thermal energy but also solar energy for electricity generation. |
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