High-performance Of Perovskite Solar Cells Based On Different Electron-transporting Layers

Perovskite solar cells have attracted widespread attention due to the rapid increase in power conversion efficiency(PCE).Within a few years,this photovoltaic technology has achieved more than 23%certification efficiency on a laboratory scale.The improvement in photovoltaic performance of perovskite solar cells is mainly attributed to the inherent properties of organic halide perovskite such as tunable band gap,high optical absorption coefficient and high carrier mobility.An electron-transporting layer and a hole-transporting layer are usually used in perovskite solar cells to separate and collect charge carriers generated in the perovskite absorber.Among them,the electron-transporting layer is essential for achieving efficient and stable perovskite solar cells.Especially,the electrical and optical properties of the electron-transporting layer can significantly affect the performance of the perovskite solar cells.So far,TiO2 is a widely used electron-transporting layer in n-i-p structure perovskite solar cells.However,the optical and electronic properties of TiO2 still have some shortcomings,which limits its commercial development.For example,the low electron mobility of TiO2 and the surface adsorption of oxygen and ultraviolet light are likely to affect the long-term stability of the perovskite solar cells and restrain the further improvement of the device efficiency.In order to solve these problems,the research work of this thesis is mainly to modify or replace the TiO2 to improve the film quality of perovskite and the power conversion efficiency and stability of perovskite solar cells.The main contents of this thesis are listed below:1.Perovskite solar cell with double layer electron transport layer was prepared by using modified TiO2 via n-doped fullerene of Bis(1-[3-(methoxycarbonyl)propyl]-1-phenyl)-[6,6]C62(Bis-PCBM).DMC plays a series of roles in regulating the energy levels,improving the electron mobility,and improving the conductivity of Bis-PCBM films.And the smooth surface morphology of Bis-PCBM:DMC composite film can be used as an excellent underlayer for subsequent deposition and growth of perovskite layer.In addition,Bis-PCBM:DMC composite film also has a stable three-dimensional skeleton a good solvent resistance,which can slow down the degradation process of the perovskite layer,improve the overall device performance including the cell stability2.In addition to modifying TiO2,this paper attempts to select a new electron-transporting layer SrGeO3 directly replaces TiO2 as an electron-transporting layer.The perovskite-type material SrGeO3 is synthesized by low-temperature hydrothermal method,and it is used as an electron-transporting layer for the first time in perovskite solar cells.Firstly,the composition and purity of the synthesized msaterials were characterized,and then the conductivity of materials were tested.The results show that the conductivity of SrGeO3 is larger than that of TiO2.The energy levels of synthesized SrGeO3 also matches well with the energy levels of the perovskite layer.Which indicates that SrGeO3 is suitable for acting as electron-transporting layer for perovskite solar cells.Finally,the perovskite solar cells based on SrGeO3 electron-transporting layer achieved a PCE as high as 17.68%with good stability.3.In this paper,a solution-treated NaTaO3 film was used as the electro-transporting layer to prepare a perovskite solar cell.The water-dispersible NaTaO3 nanoparticles was synthesized by two-step hydrothermal method.The size of NaTaO3 nanoparticles varies from 5 nm to 40 nm,with good solution dispersion and high transmittance.The resulting device presented a PCE of 18.82%.By inserting a thin PCBM layer as a modified layer of NaTaO3,the PCE could approach to 20.02%.By using NaTaO3 as the electron-transporting layer,the prepared perovskite solar cell not only had a large improvement in efficiency,but also demonstrated excellent ultraviolet stability.