Fabrication And Enhanced Performance Of Micro/nano-Structure Photoanods Based On Zn、Sn-based Oxide For Dye-Sensitized Solar Cells

In recent years, great progress has been achieved in dye-sensitized solar cells (DSSCs). To date, DSSCs employing porous titania nanoparticles have shown the highest power conversion efficiency value over12%. The semiconductor film electrode is one of key components for DSSCs and its microstructures have direct effect on the light-harvesting and electron collection, subsequently relate to short-circuit current, and finally determine the conversion efficiency. In this dissertation, considered from photon capture, electron collection and other aspects, the design construction and modification of DSSCs photoanode’s microscopic appearance structure are carried out, hoping to further raise electro-optical transfer efficiency. Further, develop new micro/nanostructured photoanode materials suitable for the flexible DSSCs.(1) Considered from photon capture, a series of hierarchical semiconductor have been synthesized to improve the conversion efficiency of DSSCs.(a) Porous nanosheet-assembled ZnO microspheres were synthesized via one-pot hydrothermal treatment followed by calcination and were used as photoanodes DSSCs. An overall light conversion efficiency of up to5.16%has been achieved with this unitary material and structure. Superior to the referenced porous dispersed ZnO nanosheets;(b) Hexagonal nanoplate-textured micro-octahedron Zn2SnO4was synthesized with the assistance of L-tryptophan. In comparison with as-prepared atactic particles, the complex architecture proves to be favorable for enhancement of overall DSSCs light-conversion efficiency via enhancement of electron transport along the nanoplate; (2) A unique Zn-doped SnO2nano-echinus, characterized by nanowire-covered mesoporous spheres, was successfully synthesized in a binary ethylenediamine (En)/water solvent system using a solvothermal route. Zn doping into the SnO2framework also induces a negative shift in the flat-band potential (VFB) and increases the isoelectric point. Consequently, the DSSCs employing Zn-doped SnO2nano-echinus photoanodes exhibit higher open-circuit photovoltages, larger short-circuit currents, longer electron lifetimes, and increased dye loading than their undoped SnO2counterparts. The energy-conversion efficiency4.15%is achieved with4.95at.%Zn-doped SnO2photoanodes, a nearly three-fold improvement compared to undoped SnO2photoanode DSSCs (1.13%); N-SnO2mesoporous microspheres with a high surface area were synthesized in an ethylenediamine (En) solvent system using a one-pot solvothermal route. These spheres are micrometer-sized and consist of packed nanobeads with diameters of～10nm. DSSCs employing N-SnO2microspheres photoanodes exhibit a high overall power conversion efficiency of2.3%, nearly116%improvement compared to commercial nanoparticle photoanode DSSCs.(3) Zn2SnO4nanowire arrays were grown onto a stainless steel mesh (SSM) in a binary ethylenediamine/water solvent system using a solvothermal route. The SSM-supported ZnSnO4nanowire was utilized as a photoanode for fabrication of large-area (10cm×5cm size as a typical sample), flexible DSSCs. The synthesized Zn2SnO4nanowires exhibit great bendability and flexibility, proving potential advantage over other metal oxide nanowires such as TiO2, ZnO, and SnO2for application in flexible solar cells. Relative to the analogous Zn2SnO4nanoparticle-based flexible DSSCs, the nanowire geometry proves to enhance solar energy conversion efficiency through enhancement of electron transport.