Fabrication Of Perovskite Solar Cell With A Gradient Band Structure And Its Performances

With the development of science and technology,the demand for energy continues to rise.In recent years,perovskite solar cells have become a research focus in the energy field due to their advantages of high conversion efficiency,simple fabrication process,and low cost.In order to achieve industrialization,on the one hand,the device needs to have better performance;on the other hand,the device needs to have higher stability to adapt to various application environments.We mainly focus on the high-performance perovskite solar cells,and improve the performance of the cells by optimizing the fabrication process of the materials and the design of the energy band structure.The specific research contents and results are as follows:(1)Exploring and optimizing the fabrication process of planar structure perovskite materials by immersion method and solid phase method.First,we used the solution immersion method to fabricate planar structure perovskite materials,and specifically explored the effect of immersion time and MAI concentration on the quality of perovskite materials.It is found that increasing the immersion time can promote the conversion of PbI2 to perovskite,but when the immersion time exceeds 5min,increasing the immersion time has little effect on the conversion of PbI2.The concentration of the MAI solution has a great influence on the quality of the material.At low concentrations,the crystal grows relatively slowly and the grain size is large,but it is prone to problems with low conversion of PbI2 and discontinuous films.At high concentrations,the film exhibits a more uniform morphology,but the grain size is smaller.Generally speaking,the fabrication of planar structure perovskite materials by the immersion method is prone to residual lead iodide,which is not conducive to the fabrication of high-performance planar structure perovskite solar cells.Therefore,we continued to research the solid-phase growth method.We explore the effects of spin coating speed,loading time and substrate temperature on the quality of perovskite materials.It is found that when the rotation speed is 6000 rpm,the loading time is 20 s,and the substrate temperature is 60℃,the device with the highest efficiency of 16.8%was obtained.(2)Developing a new kind of perovskite solar cell with a gradient band structure.We fabricated the lead halide precursor layer with graded material composition by means of alternating thermal evaporation.Through the above solid phase fabrication process,the perovskite solar cell with a gradient band structure was obtained.The results show that the addition of Br to the lead iodide precursor layer can indeed change the composition of the perovskite material,thereby achieving energy band modulation in the perovskite material.In addition,the gradient energy band structure greatly reduces the carrier lifetime and improves the carrier separation efficiency.The average power conversion efficiency of the perovskite solar cell with a gradient band structure is 17.5%,and the highest efficiency reached 18.2%.Compared with the traditional device,the efficiency was improved by 1～2%.