| In recent years,perovskite solar cells have attracted much attention due to their excellent power conversion efficiency.Among all kinds of strategies to improve the performance of perovskite solar cells,the effective results of passivation strategy have been certified by many papers.The specific work of this paper is as follows:(1)Through analyzing and researching,PMMA/MAPbI3 interface model and EDTA/MAPbI3 interface model are established.And then the interface properties of perovskite layer and passivation layer are analyzed based on the first principle.It is found that the main sources of the surface electronic states of PMMA/MAPbI3 interface system are the 1s orbit of H atom,the 5p orbit of I atom,the 2p orbit of O atom and the 6p orbit of Pb atom.The electronic states at the Fermi level of EDTA/MAPbI3 is mainly caused by orbital hybridization of the 1s orbit of H atom,5p orbit of I atom,2p orbit of O atom and 6p orbit of Pb atom at the interface.There is almost no difference between the two different interface systems.Compared with the density of states at Fermi level,PMMA has even fewer electronic states.Thus,it can be inferred that the complexation of lead ions in passivation is not affected by the complexation ability of passivation layer materials.At the same time,the more complex molecular structure may bring more interface electronic states,therefore weaken the passivation effect.Based on the micro level,the calculated analysis results can establish a good theoretical basement for the experiment therefore help guide the next step of the experiment.(2)Through the preparation and testing of perovskite solar cell devices with different passivation layers,the effects of different thickness of passivation layer and different solvents on the photoelectric properties of perovskite solar cell devices were studied.It is found that only the ultra-thin passivation layer can improve the overall performance of the device.At the same time,the solubility,polarity and functional group of the solvent should be taken into account when selecting the solvent for the passivation layer.If the polarity of the solvent is similar to that of perovskite,the polarity can bring better wetting effect.At the same time,if the solvent has proper functional group,it may further improve its performance.Combined with the simulation results,one of the mechanisms of PMMA passivation can be attributed to the main functional groups of PMMA,which can well combine the electronic defects such as Pb2+ gap and reduce the defect density.At the same time,it can provide arc pair electrons to the Pb2+empty orbit,therefore passivate the hanging bond on the surface of perovskite layer.Then the passivation layer helps reduce non radiation recombination,so significantly improve the overall performance of the device.The other passivation mechanism is that the PMMA layer can effectively restrain photogenerated electrons transferring to the hole transport layer.After adding different passivation layers,the open circuit voltage increased from 0.86 eV to 0.89 eV,increased by 3.49%;the short circuit current increased from 20.18 mA/cm2 to 22.36 mA/cm2,increased by 10.80%;the filling factor increased from 58.59%to 79.40%,increased by 35.52%.In this paper,the passivation theory and strategy of perovskite solar cells are deeply discussed,which provides a reference for the specific designation of passivation strategy to improve the performance of perovskite solar cells. |
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