Study On Preparation And Properties Of Solar Cell Using ZnSe Quantum Dot Sensitized Nano-TiO₂ Photoanode

Scientists remain focused on developing and utilizing various solar cells for more than a century,because solar energy is inexhaustible and green enviromental protection as a type of renewabl energy.In recent years,quantum dot-sensitized solar cells?QDSSCs?have attracted the attention of researchers because of QDSSCs'high theoretical conversion efficiency and low cost.However,this high efficiency has not been experimentally achieved.And some harmful quantum dots such as CdTe,CdSe,and PbS are commonly used for the sensitizer.In our study,ZnSe quantum dots was used as sensitizers,and La-doped nano-TiO₂ was used as a substrate materials,for preparing the ZnSe quantum dot-sensitized nano-TiO₂ photoanode solar cells.The photoelectronic and electrochemical properties of the QDSSCs were studied.In the experiment,La-doped mesoporous TiO₂ powders were prepared by sol-gel method,and nano-TiO₂ thin film was prepared by a spin-coating.ZnSe QDs were prepared at room temperature by using an aqueous phase synthesis method.On this basis,chemical bath deposition?CBD?method was used for preparing the nano-composite film of the ZnSe QDs sensitizer and the nano-TiO₂ substrate.In the assembly solar cell,the nano-composite material,a redox pair S^2-/S_n^2-,and Cu₂S were used to photoanode,polysulfide electrolyte,and counter electrode,respectively.The photoanode prepared were characterized by X-ray diffraction?XRD?,N₂sorption-desorption isotherms,scanning electron microscopy?SEM?,Fourier transform infrared?FT-IR?spectroscopy,ultraviolet-visible?UV-VIS?absorption spectroscopy,steady state surface photovoltage?SPV?spectroscopy,and transient photovoltage spectroscopy?TPV?.The electrochemical properties of the prepared QDSSCs were characterized by an electrochemical workstation.The experimental results show that the La-doped mesoporous TiO₂ nanocrystals has an anatase structure with large specific surface area and pore volume,and its pore size distribution is about 26 nm,which belongs to a typical mesoporous material.The nano-TiO₂ film has an uniform porous structure on the surface.Both the nano-TiO₂ powder and the nano-TiO₂ thin film exhibit a strong absorption characteristics in the wavelength range of 300-400 nm and n-type surface photovoltaic characteristic.The core-shell ZnSe QDs prepared at room temperature have a cubic sphalerite structure with the average grain size of 3.5nm.As compared with the UV-VIS absorption spectrum of the conventional ZnSe,the first exciton peak of the ZnSe QDs shows an obvious blue shift,,and the optical bandgap of the QDs becomes bigger,resulting in an obvious quantum size effect.The first exciton absorption peak of the ZnSe QDs appears at the range of 380-700nm.The QDs shows n-type surface photovoltaic chracteristc similar to the nano-TiO₂.As compared with the unsensitized nano-TiO₂ thin film,the ZnSe QDs-sensitized TiO₂ thin film was more smooth and intensive,and the ranges of both UV-VIS absorption and SPV response were greatly widened,which may result in effective use of solar energy.The conversion efficiency of the QDSSCs is 2.61%when Zn?CH₃COO?₂ was used as a precursor for cations,the number of laryers of the nano-TiO₂ substrate film was 4?its thickness is about 24.61?m?,and polysulfide electrolyte concentration was 0.2M Na₂S and 0.2M S.