Study On Mesoscopic Perovskite Solar Cell

With the rapid development of perovskite solar cells, the structure of perovskite solar cell(PSCs) has evolved from the initial dye sensitized solar cells(DSCs) to the structure of mesoporous perovskite solar cells(MPSCs) and the structure of planar perovskite solar cells(PPSCs). In the process of improving MPSCs performance, the method of depositing the perovskite absorbers develops gradually from one-step spin coating for two-step spin coating, and then dual-source thermal evaporation method and vapor-assisted solution deposition method. However, the cost of vapor deposition method is too high, which is not suitable for the large-scale preparation of PSCs. So the method of spin coating is favored by people, and the performance of the PSCs has become the focus of the research by improving the crystallization and morphology of the perovskite absorption layer.In this thesis, basing on the structure of MPSCs, we designed the experiments of improving the performance of the PSCs by improving the crystallization and morphology of the perovskite absorption layer, which mainly includes the following three aspects:(1) In order to determine the optimal preparation method of perovskite absorption layer, we designed the experiments of preparing the perovskite by one-step spin coating and two-step spin coating on the mesoporous layer. The performance of MPSCs prepared by the two-step method is much higher than that of the one prepared by the one-step method. When the MPSCs was prepared by one-step method, the optimal current density(JSC), open circuit voltage(VOC), fill factor(FF) and the efficiency of solar cell reached 5.78 m A/cm2, 788 m V, 40.18%, 1.83%, respectively. When the MPSCs was prepared by two-step method, the optimal current density(JSC), open circuit voltage(VOC), fill factor(FF) and the efficiency of solar cell reached 7.10 m A/cm2, 828 m V, 60.38%, 3.55%, respectively. The efficiency of the latter is significantly higher than that of the former.(2) Improve the crystallization and morphology of the perovskite absorption layer. First, we designed the experiments of preparing MPSCs under condition of heating substrate under different temperature before depositing the Pb I2 layer, and studied the effect of heating temperature on the performance of MPSCs. Then, we designed the experiments of preparing MPSCs under the condition of different deposited time after depositing the Pb I2 layer, and studied the effect of deposited time on the performance of MPSCs. Through the characterization of the photo-anode material and the performance tests of cell, it is found that the substrate heating and deposited time can promote the crystallization of the perovskite and increase the uniformity of the thin film, so as to improve the carrier collection and reduce the electron-hole recombination, and greatly improve the photo-current and efficiency of solar cells.(3) On the basis of previous experiments, we have designed the experiment of Cl doped Pb I2 to achieve the purpose of Cl doped perovskite. Through the characterization of the photo-anode material, it is found that the absorption strength of the photo-anode increases after Cl doped Pb I2 to prepare the perovskite absorber layer. And the short circuit current density of the corresponding solar cell increases, the efficiency and IPCE are improved too. This shows that the charge transport in the solar cell is enhanced, and the performance of cells can be improved by Cl doping.