Synthesis Of Semiconducting Copper-based Chalcogenide Nanostructures For Solar Energy Conversion Applications

Copper-based chalcogenide semiconductors are promising solar energy conversion materials due to their merits of suitable bandgap（1-2 eV）,high absorption coefficient,environment friendly constituting elements,and low cost.The materials show great potential in solar energy conversion devices.In this thesis,a series of Cu_2-xS,Cu_2-xSe,CuInS₂（CIS）,and Cu₂ZnSn(S_1-xSe_x)₄（CZTSSe）have been controllably synthesized and demonstrated as efficient electrodes for quantum dots-sensitized solar cells（QDSSCs）and photoelectrochemical（PEC）water splitting.Main results are summarized as follows:（1）A simple metal complex mixing（Metcomix）process for preparing multinary Cu₂ZnSn(S_1-xSe_x)₄ nanocrystals in aqueous and at room temperature is researched.[Sn₂S₆]^4-and[Sn₂S₄Se₂]^4-complex are designed creatively to balance the reaction rates between metal cations and chalcogen anions in aqueous solution,and consequently overcomes the big challenges of easy formation of binary impurities.Further more,we regulate different components of the Cu₂ZnSn(S_1-xSe_x)₄ to investigate the influences to the water splitting device.Experimental data shows that the ZnO/CZTS and ZnO/CZTSSe photoanodes exhibit optimal ABPE of 2.80%and 3.43%,respectively.（2）A green,pollution-free and low-cost method is used to synthesize CuInS₂nanocrystals.This method has the characteristics of simple synthesis process,large amount of production,zero energy consumption,low cost and without any pollution.The CIS nanocrystals have a small size of 2 nm and exhibit remarkable room-temperature photoluminescence and optical absorption properties.The CIS nanocrystals yield an emission peak at 813 nm,and the applied bias photon-to-current efficiencies（ABPE）for ZnO/CIS photoanodes is 3.05%.（3）A route for controllably synthesizes single-and double-shelled Cu₇S₄ and Cu₂-_xSe nanocages is researched in this thesis.These hollow nanocages are then used as CE materials in QDSSCs to investigate the influences that have a double-shelled instead of a single-shelled structure.The QDSSCs which have double-shelled CEs exhibit larger fill factor and short-circuit current density and higher PCEs.This owes to their increased CE-electrolyte interface for smaller charge transfer resistance and faster redox regeneration.The results show that PCEs of 4.76%for the double-shelled Cu₂-_xSe nanocages and 4.53%for the double-shelled Cu₇S₄ nanocages.