Effects Of Interface Modification And Optimization Of Active Layer On The Properties Of Perovskite Solar Cells

After 2000,the new generation of solar cells rose rapidly.Perovskite solar cells have become the star in the field of photovoltaic research,the power conversion efficiency since 2009,from 3.8% to 22.1%,completed the leap of other solar cells for decades,it is still a lot of room for improvement.Therefore,how to improve its photoelectric conversion efficiency is still an important issue in the field of perovskite solar cell research.Firstly,Based on the related literature and predecessors’ work,this paper makes the basic perovskite solar cells to provide a platform for its optimization.Secondly,the cathodic buffer layer is introduced to improve the interfacial engineering of perovskite solar cells,and then the optimization mechanism is analyzed from the viewpoint of intuitionistic physical.Finally,the quality of PbI₂ film is improved by the change of mixed solvent and annealing method,and the quality of perovskite crystal is optimized to improve the performance of the device.In the second chapter,the basic perovskite solar cells were made by using the modified two-step spin coating method to make the perovskite active layer with the structure of ITO / PEDOT: PSS / CH₃NH₃PbI₃ / PCBM / Ag.The open circuit voltage（Voc）is 0.97 eV,the short circuit current density（Jsc）is 17.91 mA · cm²,the filling factor（FF）is 57.41%,and the power conversion efficiency（PCE）of the device reaches 9.97%.In the third chapter,the influence of different thickness of Bphen on the photoelectric properties of perovskite solar cells was studied.The structure of the device was ITO / PEDOT: PSS / CH₃NH₃PbI₃ / PCBM / Ag.It was found that the insertion of the cathode buffer layer improved the surface morphology of the active layer film,formed a good ohmic contact with the cathode,and optimized the performance of the device.When the thickness of Bphen is 10 nm,the open circuit voltage（Voc）is 0.96 eV,the short circuit current density（Jsc）is 21.92 mA · cm²,the filling factor（FF）is 66.24%,and the power conversion efficiency（PCE）is 13.91%.The efficiency is improved by nearly 40% compared to the 9.97% of devices that without the cathode buffer layer.In the forth chapter,the effect of different ratios of DMF and DMSO on the crystallization rate of PbI₂ was studied to analyze the photoelectric properties of the perovskite solar cells.Because of the strong intermolecular coordination between DMSO and PbI₂,the PbI₂ crystals can be inhibited to a certain extent.When the CH₃NH₃ I solution is spin-coated,the PbI₂-DMSO-CH₃NH₃ I mesophase can be formed to promote the full reaction of PbI₂ with CH₃NH₃ I,therefore the quality of perovskite crystals enhances.The results showed that the addition of DMSO in DMF was beneficial to the improvement of the quality of perovskite crystals.In addition,in order to further reduce the crystallization rate of PbI₂ and increase the quality of perovskite crystals,the annealing conditions of PbI₂ solution with different ratio of mixed solvent were changed to stand in nitrogen environment.And its influence on the photoelectric properties of the perovskite solar cells was analyzed.The results show that the inhibition of PbI₂ crystal is enhanced under the standing condition,and the PbI₂ film is optimized to promote the improvement of the perovskite crystal quality.Under the standing condition,when the mixing ratio of DMSO is 40%,the device performance is the highest,and the short circuit current density（Jsc）reaches 20.23 mA / cm²,and the power conversion efficiency（PCE）of the device is 13.23%.Compared to the basic device efficiency of 9.43%,efficiency increased by more than 40%.