| One dimensional nano array exhibits excellent photoelectric properties superior to bulk counterpart due to unique structure features, such as high specific surface area and direct carrier transport channel, and has been widely used in the applications of photoelectronic devices, solar cells and photocatalysis. Pyrite FeS2 has been regarded as a promising photovoltaic material because of its suitable bandgap (0.95 eV), extremely high optical absorption coefficient, abundant storage of component elements, environmental friendly feature and low fabrication cost. However, FeS2 materials have some common problems, for instance, impurity phases, defects and non-stoichiometric ratio. As a result, photovoltaic devices based on FeS2 show low photoelectric conversion efficiency. Therefore, beside searching for high-purity and high-quality FeS2 preparing methods, it is required to enhance material performances by other perspective, namely, structure design. Some successful samples from one dimensional semiconductor systems, such as Si, CdTe, and CdS/Cu2S, have suggested that one dimensional nanostructures possess various excellent properties over planar geometries in many application fields. Therefore, this paper put forward a method based on ZnO template for the synthesis of one dimensional FeS2 and its composite nanostructures to improve the photoelectric properties.ZnO nanorod arrays were grown on seed-coated FTO substrate via hydrothermal method. The effects of parameters such as seed layer, colloid concentration, different substrates and precursor concentration on vertical alignment of the arrays were studied. We defined a parameter named alignment degree, and showed a simple mathematical statistics technique to calculate the parameter. Experimental results showed that seed layer played a key role in the vertical alignment of arrays; the surface roughness of substrates could influence the alignment of arrays; altering colloid concentration could controll array alignment; precursor concentration had week effect on the array alignment, but could adjust the diameter and aspect ratio of nanorods.Orderly aligned pyrite FeS2 nanorod arrays and FeS2 nanotube arrays were prepared using ZnO nanorod arrays as template and via different solution immersion treatment and subsequent sulfurization process. The composition, structure and morphology of one dimensional FeS2 nanostructures films were characterized, and the light absorption, photoresponse and electrochemical properties were systematically studied. A comparison of the photoelectrochemical properties between one dimensional structured FeS2 films and nanoparticle structured FeS2 films, and the effect of one dimensional structure on material’s properties were researched, a mechnism was proposed to explain the reason. Two different FeS2 nanostructure films both exhibited excellent light absorption. In comparison with nanoparticle structure, one dimensional structure showed better photoelectric properties, higher corrosion resistance and electrochemical stability.ZnO/ZnS/FeS2 composite nanorod arrays were obtained by solution treatment and subsequent sulfurization on ZnO nanorod arrays. Abundant characterization methods were performed on the composition, structure and morphology of the ternary composite films. Some misfit dislocations were observed at the ZnO/ZnS interface by high resolution TEM. It is found that ZnO has epitaxial relationship with ZnS. Deep research was made on the photoluminescence, light absorption and irradiation stability of ZnO/ZnS/FeS2 nanorod arrays. It is found that FeS2 sensitization could enhance the visible light absorption and photoresponse performances of wide bandgap semiconductors. This mainly benefited from the excellent light absorption of FeS2 quantum dots and gradient heterostructure formed in ZnO/ZnS/FeS2 system. ZnO/ZnS/FeS2 displayed good irradiation stability.Various solar cells were constructed using different photoanodes with Pt counter electrode and using ZnO/ZnS/FeS2 photoanodes with different counter electrodes. Cell performances were tested, and the effect of photoanode and counter electrode on cell performance were analyzed. Quantum-dot sensitized solar cell using ZnO/ZnS/FeS2 as photoanode and using Pt as counter electrode showed relatively high performances, but the efficiency was still lower than other types of solar cells. This may be related to cell assembling procedures, electrode structure, electrolyte system and some other factors. |
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