Optimization Of SnO₂ As Electron Transport Layer In Perovskite Solar Cells

With the rapid development of society and economy,the demand of energy is rising sharply,and the total amount of energy consumed every day is also increasing.Therefore,the energy crisis caused by excessive energy consumption and insufficient reserve energy has attracted widespread attention.Since 2019,halide perovskite,as an unprecedented semiconductor material,has become a hot research topic.Perovskite solar cells take ABX₃ material as the core,used as light absorption layer,having direct and adjustable band gap,high electron and hole mobility,strong light absorption coefficient,high defect tolerance and low non-radiative recombination.In addition,perovskite solar cells can be spin-coated at room temperature,roll-to-roll printing and manufacturing can be realized commercially.In recent years,researchers have studied the mechanism of perovskite solar cells,hoping to make a breakthrough in this field and at the same time promote the commercialization of perovskite solar cells.A large number of early experiments have shown that the passivation of the perocskite soalr cells interface layer can not only improve the efficiency of the cells,but also improve the hysteresis of the cells.As a commonly used electron transport layer material,SnO₂ has high electron mobility,can be prepared at room temperature,and matched the energy level of perovskite.However,it can be seen from the experimental results that this electron transport layer material also has its own shortcomings.There are oxygen vacancy defects in the SnO₂ body and a large number of hydroxyl groups on the surface of the film,therefore the efficiency of the perovskite solar cell under this system is affected,and there is hysteresis in the I-V curve.In view of these two key problems,this paper conducted a large number of experiments to target the defect passivation and regulation of SnO₂ in vivo and in vitro,and conducted in-depth research mainly through two passivation pathways:Firstly,due to the existence of oxygen vacancy defect in SnO₂,the passivation of oxygen vacancy defect in SnO₂ was successfully realized by introducing ethylenediaminetetraacetic acid（EDTA）with appropriate concentration.The maximum efficiency of this experiment was 18.59%.Secondly,a layer of fullerene derivative(C₆₀-SAM)was modified on the surface of the prepared SnO₂ thin film to improve the hysteresis of the device.The modified fullerene derivatives can neutralize with the hydroxyl groups on the surface of SnO₂,thus reducing the number of hydroxyl groups on the surface,improving the extraction capacity of charge carriers and the film forming quality of perovskite films.The final improvement of the device’s hysteresis is mainly due to the improvement of the filling factor of the cell modified by C₆₀-SAM.For perovskite cells in this system,the optimal modification concentration of fullerene derivatives is 1 mg/m L,and the minimum hysteresis factor（HI）of the cell is 0.058.Finally,this paper also combined EDTA and C₆₀-SAM into SnO₂ to achieve efficiency improvement and further reduction of the hysteresis factor.The final efficiency is close to 19%,and the hysteresis factor is 0.028.In conclusion,this paper improves the perovskite solar cell from the aspects of defect passivation and regulation of SnO₂ electron transport layer,and provides experimental guidance for defect passivation of perovskite solar cells.