Preparation And Application Of Chalcogenide Semiconductor In Solar Cells

With the increasing depletion of fossil fuels, the development of clean and renewable energy hasbecome a necessary common topic in the world. In this dissertation, solar cells, as one of new energies,have attracted great attentions. Because nanocrystals offer the impressive ability to photoelectricconversion performance, low cost and ease of fabrication, nanocrystals-sensitized solar cell has turned to bethe most popular one in solar cells. The optimization of the sensitizer can improve the photoelectricconversion efficiency, while the development of the counter electrode can reduce the cost of the solar cells.In order to improve the development of large-scale industrial production process, we investrated thepreparation of chalcogenide semiconductors and their application in this dissertation.In this dissertation, the main contents as follows:In chapter2, it is the first time to prepare wurtzite phase CuInS₂nanocrystals with sphere-likemorphology via a simple route in aqueous solution under atmospheric conditions. XRD, XPS, EDS,TEM and HRTEM confirm the structure, composition and morphology of as-obtained nanocrystals.The UV-vis absorption spectra reveals that the wurtzite CuInS₂NCs have stronger optical absorptionthan chalcopyrite-phase in the visible light region. The band gap of wurtzite CuInS₂NCs is determinedto be1.47eV which is optimal for photovoltaic applications. The CuInS₂NCs were synthesized inwater under atmospheric conditions without longfat chains of organic ligand. The easy preparation andlow cost nature of solvothermal method make it quite attractive in solar cell application.In chapter3, we mainly used the two different kinds CuInS₂nanocrystalline which were synthesizedin chapter2as experimental material to prepare the counter electrode of dye-sensitized solar cells. Wefound the annealing temperature had a great impact on the crystal structure of CuInS₂nanocrystalline filmby XRD analysis. High densely and flat film were prepared by drop casting method. All results indicate thatthe CuInS₂material can be applied in counter electrode in DSSCs.In chapter4, we used the CuInS₂QDs which were synthesized in chapter2as sensitizers, TiO₂nanorod arrays as photoanode to assemble and install QDSSCs. Through the analysis of the experimentalresults we can see the method is feasible which the water phase synthesis CuInS₂quantum dots were used for sensitized TiO₂nanorod arrays for quantum dot-sensitized solar cells.In chapter5, we have successfully used CdS and PbS QDs as co-sensitizers to improve theperformance of QDSSCs. In comparison to single QDs sensitized QDSSCs, the CdS/PbS co-sensitizedphotoelectrode showed substantially improved overall photoconversion efficiency. The efficiency of theCdS/PbS co-sensitized solar cell is as high as2.02%under one sun illumination （AM1.5,100mW/cm²）.And a cascade structure of QDs co-sensitized mechanism was proposed. This work also demonstrated thepotential applications of CdS/PbS co-sensitized TiO₂nanorod arrays for QDSSCs. More importantly, theproposed co-sensitized CdS/PbS QDSSC fabrication approach offers low-cost and easy preparation nature,and this device can reach better photovoltaic performance. We believe that this proposed approach mayhave great potential to be applied in high efficiency, yet low cost photovoltaic field.