ZnO不同微结构/ZnFe_2O_4复合薄膜光生电荷热动力学与光电性质研究

采用不同方法分别制备出ZnO纳米颗粒、纳米线、纳米棒、纳米管4种微结构,以ZnFe2O4为无机染料敏化剂在ITO透明导电玻璃上制备成ZnO不同微结构/ZnFe2O4异质结.XRD检测结果表明,所有复合结构中两种组分都达到了良好的结晶状态;而且,各复合薄膜体系都呈现出了异质结复合结构的光吸收特性,但光吸收性质差异不明显.稳态表面光电压谱测试结果表明,各异质结构都呈现出优于单一组分的光伏响应特性;而且,4种异质结构光伏性质呈现出:ZnO纳米管/ZnFe2O4ZnO纳米棒/ZnFe2O4ZnO纳米线/ZnFe2O4ZnO纳米颗粒/ZnFe2O4的特点.在较弱正外电场诱导下,复合薄膜仍然保持稳态下的光伏响应特性;随着外电场逐步提高,ZnO纳米颗粒/ZnFe2O4光伏性质增加非常明显,在+2V电压诱导下,ZnO纳米颗粒/ZnFe2O4已接近ZnO纳米管/ZnFe2O4的光伏响应强度,并明显高于另外两种异质结构的光伏性质.从光阳极微结构、自由电荷扩散长度、空间电荷区厚度、载流子参数、内建电场和能级匹配几个方面,详细讨论了ZnO/ZnFe2O4异质结中光生电荷分离的影响因素以及光生电荷传输机制.

Study of Thermodynamics of Photogenerated Charges and Photoelectric Properties in Different Microstructures ZnO/ZnFe_2O_4 Composite Films

ZnO films with several microstructures including nanoparticles,nanowires arrays,nanorods arrays and nanotubes arrays were prepared with different methods.With ZnFe2O4 as inorganic sensitizer,different microstructures ZnO/ZnFe2O4 heterojunctions were fabricated on ITO conductive glass.The results of XRD show that ZnO and ZnFe2O4 components can be indexed as the well-crystallized structures for each heterostructure.Moreover,all of composite films present the absorption characteristics of the composite structure,but there is not the obvious difference for these absorption spectra.The signals of steady state surface photovoltage spectroscopy indicate that all of composite heterostructures exhibit the higher photovoltaic response than two components.For different ZnO/ZnFe2O4 heterojunctions,the photovoltaic responses present that ZnO nanotubes/ZnFe2O4 is higher than ZnO nanorots/ZnFe2O4,ZnO nanorots/ZnFe2O4 higher than ZnO nanowires/ZnFe2O4,ZnO nanowires/ZnFe2O4 higher than ZnO nanoparticles/ZnFe2O4.Under the lower positive bias,all of composite films exhibit the same photovoltaic signal as the steady state.With the bias increasing,the surface photovoltage of ZnO nanoparticles/ZnFe2O4 enhances quickly.Under the bias of+2V,the photovoltaic signal of nanoparticles/ZnFe2O4 is similar with ZnO nanotubes/ZnFe2O4,and higher than other heterojunctions.From the microstructures of anodes,diffusion length of free charge,thickness of surface space charge region,carrier parameters,build-in electric field and energy level matching,we analysed in detail the separation process and the transport mechanism of photogenerated charges in ZnO/ZnFe2O4 heterojunctions.