Study On Optimization Of Charge Transport Performance In Carrier Transport Layer For Two-dimensional Perovskite Solar Cells

Since perovskite solar cells were first prepared,their development speed has exceeded people’s expectations.Due to the advantages of high efficiency and low cost,their industrialization prospect is very promising.However,the poor environmental stability and moisture resistance of perovskite solar cells hinder its final commercialization.Due to the high stability of two-dimensional perovskite materials,the above problems are well overcome and coursed new expectations for the application of perovskite photovoltaic devices.In addition to change the chemical structure to obtain better stability and device efficiency,more effective method is to improve the charge transfer performance by optimizing the crystal orientation,energy level matching and interface characteristics of the charge transfer layer.In view of the above problems,a lot of research work has been done on the morphology control,defect passivation and solvent optimization to the charge transfer layer of the trans-two-dimensional perovskite solar cells（referred to as‘two-dimensional perovskite device or two-dimensional device’）.In this Thesis,the specific work includes the following points:1)The effect of polymer PFN containing hydrophobic groups on the performance of two-dimensional device based on PCBM electron transport layer was studied.It is found that the introduction of PFN improves the inter-layer interface contact of the two-dimensional device,the inter-layer energy level matching is better,and the surface defects of perovskite layer are passivated.The photoelectric properties and environmental stability of two-dimensional devices are significantly improved.The photoelectric conversion efficiency increased by 62.8%and the short-circuit current density increased by34.6%.The initial conversion efficiency of the unpackaged two-dimensional device remained 89.5%after 1000 h in the environmental stability test,which was 37.7%higher than that of the control group.2)The perovskite layer of the two-dimensional device was prepared by one-step deposition method.The PCBM solution was used as the anti-solvent,and the perovskite-PCBM heterogeneous film was directly formed by dropping the perovskite layer during the spin coating process.The perovskite thin films prepared by one-step deposition method are dense and uniform,and the surface defects are effectively passivated by adding PCBM.The quality of the thin films is improved,and the coverage rate of the thin films is significantly improved.The photoelectric performance of the two-dimensional device prepared by one-step deposition method was significantly improved:the photoelectric conversion efficiency reached 12.8%,which was significantly higher than that of the device prepared by conventional method（8.0%）,and the environmental stability was significantly enhanced.3)The composite double-layer charge transfer layer is introduced into the preparation process of two-dimensional devices.Organic semiconductor material C₆₀was deposited on PCBM electron transport layer to prepare PCBM/C₆₀composite electron transport layer.The C₆₀electron transport layer not only makes the two-dimensional devices form a more relaxed energy level arrangement,which is conducive to the transmission and collection of charges,but also can effectively increase the film coverage and passivate the surface defects of PCBM electron transport layer.The photoelectric parameters of two-dimensional devices based on PCBM/C₆₀composite electron transport layer are significantly improved,and the photoelectric conversion efficiency is increased by 58.2%.The hysteresis phenomenon was effectively suppressed and the environmental stability was significantly enhanced.4)PTAA/MoO₃ as a composite hole transport layer to improve the performance of two-dimensional devices was studied.Two-dimensional devices fabricated by PTAA/Mo O₃hole transport layer,the energy levels of each functional layer are better matched,the charge extraction and interlayer transmission are improved,and the defects on the surface of perovskite layer are effectively passivated and the morphology is improved.The photoelectric parameters of two-dimensional devices based on PTAA/Mo O₃composite hole transport layer are significantly improved,and the photoelectric conversion efficiency is increased by 18.3%.The hysteresis phenomenon was effectively suppressed and the environmental stability was significantly enhanced.5)The effects of solvent selection of PTAA hole transport layer（toluene,chlorobenzene and 1,2-dichlorobenzene）on the performance of two-dimensional devices were studied.Through experimental verification and molecular dynamics simulation,it was found that PTAA formed obvious molecular aggregation phenomenon in toluene solvent.This molecular aggregation increases the area of the excited state charge transfer channel,which increases the probability of effective hole migration and improves the photoelectric performance of the two-dimensional device.The photoelectric conversion efficiency of the two-dimensional device based on toluene solvent was 10.1%and 6.3%higher than that of the device based on chlorobenzene and 1,2-dichlorobenzene solvent,respectively,and the short-circuit current density was increased by 8.1%and 6.2%,respectively.In addition,toluene solvent can improve the hydrophilicity of PTAA layer,increase the coating coverage and density of the interface,and significantly improve the environmental stability of the two-dimensional device.The results show that the choice of solvent has a positive effect on the performance of two-dimensional devices.In the preparation of two-dimensional devices,toluene is the most suitable solvent for PTAA layer.