| People are in pursuit of a green, low carbon and environmental lifestyle. So the development of clean energy is imperative, among which solar energy shows incomparable advantages. Titanium dioxide (TiO2) is non-toxic, stable and cheap. The development of nano-technology promotes applications of nano-structured TiO2 especially TiO2 nanotube arrays in the field of water photolysis, photocatalysis and solar cells. But the application of TiO2 is seriously limited because of its wide band gap (3.2 eV), which can only absorb UV light. Therefore, TiO2 nanotube arrays are modified by narrow band gap semiconductors.Sb2S3 is a direct band gap semiconductor, and has a large absorption coefficient (1.8 x 105 cm -1) and proper optical band gap of 1.7 eV. Sb2S3 is an ideal photosensitizer.Cul is a p-type inorganic semiconductor with high hole mobility and a wide band gap of 3.1 eV. Cul shows versatile applications for solid state solar cells、light-emitting diodes、 field-effect transistors, etc. The article is based on Sb2S3/TiO2 nanotube arrays heterostructure and the main contents are as following:1. Sb2S3 was successfully deposited on TiO2 nanotube arrays through hydrothermal synthesis. Three different precursors were used to control the size and load of Sb2S3.(1) SbCl3 (HC1) and Na2S·9H2O aqueous solutions were used as precursors, the size of obtained Sb2S3 nanoparticles is from 11 to 15 nm. The Jsc and η of the Sb2S3/TiO2 nanotube arrays heterostructure are 1.42 mA/cm2 and 0.40%, respectively.(2) SbCl3 and Na2S2O3·5H2O aqueous solutions were used as precursors, hydrothermal reaction time and concentration of precursor solutions were controlled in hydrothermal reaction:Firstly,0.8 M SbCl3 and 1.6 M Na2S2O3·5H2O aqueous solution were used as precursors and the hydrothermal reaction time was changed (8h,16h,24h). When hydrothermal reaction time is 16 h, the obtained Sb2S3(16h)/TiO2 nanotube arrays heterostructure exhibits high photoelectrochemical performance. Jsc is as high as 4.10 mA/cm2, the Voc and ηis up to 0.90 V and 2.82%, respectively.Then, the concentration of SbCl3 aqueous solution was changed (1 mM,8 mM, and 16 mM), the corresponding concentration of Na2S2CO3·5H2O aqueous solution was 2 mM,16 mM, and 32 mM, respectively. When the concentration of SbCl3 aqueous solution was 8 mM, Jsc is 2.32 mA/cm2, Voc is 0.84 V, and η reached to 0.64% in the obtained Sb2S3(8mM)/Ti02 nanotube arrays heterostructure.(3) SbCl3 alcohol solution and Na2S·9H2O aqueous solutions were used as precursors, the average size of Sb2S3 nanoparticles is between 15 nm and 22 nm. The Jsc and η are 3.51 mA/cm2 and 0.66%, respectively.2. Cul was employed as hole transport material in Sb2S3/TiO2 nanotube arrays heterostructure prepared by hydrothermal method. The separation efficiency of photoinduced charge is greatly enhanced: the Jsc is increased from 1.92 mA/cm2 to 3.51 mA/cm2, and the η is increased from 0.66% to 0.95%. UV-visible absorption spectroscopy, surface photovoltage spectroscopy and photoluminescence are used to analyse the effect of Cul on the photogenerated charge behaviour in Sb2S3/TiO2 nanotube arrays heterostructure and identify the transfer mechanism of photoinduced carriers. Cul provides channels for photogenerated holes and blocks electrons. Meanwhile, Cul also absorbs photons in the UV range. |
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