The Application Of Polyoxometalates/Semiconductor Composites In Quantum Dot Sensitized Solar Cells And Photoconductivity

Quantum dot sensitized solar cells?QDSSCs?has been widely studied in the past few years because of its low cost,simple preparation and large absorption range.At present,the efficiency of the QDSSCs has reached 11%,but this is far below the theoretical efficiency.Tthe photoanode and the counter electrode are main components of the QDSSCs,in the second and the three part of this thesis,we aim to optimize the composition of QDSSCs and then to improve the the power conversion efficiency.CdS semiconductor is ?-? group compound,which has high absorption coefficient and low resistivity.Therefore,it has very important applications in catalysis,photoelectric and photoconductive materials.However,However,when CdS is excited by light,its photogenerated electrons and holes can not be separated effectively,which greatly limits its application.At present,in order to improve the photoconductivity of CdS,most of the solutions are to combine CdS with other materials,which provides more theoretical and practical basis for the application of CdS in optoelectronic devices.Polyoxometalates?POMs?are considered to be good electron acceptors.It can capture the photogenerated electrons from conduction band of the semiconductors,then it indirectly reduce the photogenerated carriers recombination rate,and improve the photoelectric and photoconductivity properties of semiconductors.In this paper,we introduce the POMs into the CdS semiconductor and the TiO2 semiconductor of photoanode in QDSSCs,and then achieve the purpose of improving the photoelectric and photoconductivity properties.In this paper,we prepared?n-Bu₄N?₃PW₁₂/TiO₂ composites by physical method,and prepared the?n-Bu₄N?₃PW₁₂/TiO₂ film electrode by doctor blade technique.QDSSCs are composed of?n-Bu₄N?3PW12/Ti O2 film electrode,CdS/CdS quantums,the polysulfide electrolyte and Pt,then we tested the performance of the cells.The results show that the photocurrent and efficiency of?n-Bu₄N?₃PW₁₂/TiO₂?10.41mA/cm2,1.29%?are higher than the pure TiO2?7.9mA/cm2,0.94%?.The MoS₂-graphene?M-G?hybrid that as the counter electrode of QDSSCs was synthesized by hydrothermal method,and the electrochemical properties of M-G counter electrode were investigated.The value of Rct and J0 for M-G counter electrode is 4.75 ? cm2 and 21.27mAcm-2 by EIS and Tafel measurements,which indicated that M-G had good electrocatalytic properties.The efficiency of the M-G electrode is 2.21%,which is higher than that of MoS₂ and Pt counter electrodes.SiW₁₁Co/CdS nanoparticles were prepared by hydrothermal method,and the composites were tested by photocurrent response and current-voltage curve measurements.Compared with pure CdS,the photocurrent of 5%SiW₁₁Co/CdS improved by about 50%,which indicated that the photoconductivity properties of the CdS were improved.