Research On The Charge Carrier Transport Mechanisms And Stability Of The Two-Dimensional Perovskite Solar Cells

In recent years,two-dimensional(2D)perovskite materials have attracted extensive attention in the field of semiconductor research due to their unique photoelectric properties and excellent chemical stability.Owing to their high open-circuit voltage and stable light-to-electric power output,2D perovskite solar cells(PSCs)fabricated by a simple solution-processing method have shown great potential for industrial development.However,the mechanisms of charge carrier transport and stability of 2D PSCs still remain elusive,which will have negative impact on their further development.Therefore,based on the recent progresses,we investigated the charge carrier transport mechanisms and stability of 2D PSCs.In order to study the carrier transport mechanisms of 2D perovskite solar cells,we focused on the factors that influence the charge carrier transport,including vertical phase distribution,bulk defects and the carrier migration behaviors,etc.In addition,the inverted planar devices based on BA2MA3Pb4I13 were fabricated and their photovoltaic performance was tested.Adopting a molecular modification process of C60 derivative(PCBM)on the BA2MA3Pb4I13 precursor,we found that compared with the pristine film,the modified BA2MA3Pb4I13 films had higher crystallinity,improved morphology,reduced trap state density and faster interfacial charge carrier transfer.In addition,we analyzed the electron migration at the 2D perovskite/ETL interface that significantly affected the built-in electric field by applying in-situ tests based on Kelvin probe force microscopy(KPFM).Consequently,the optimized charge carrier transport by the PCBM molecular modification process resulted in the increase of open-circuit voltage(VOC)and short-circuit current density(Jsc)of 2D PSCs,and the device efficiency was improved from 9.25%to 11.02%.In order to study the stability of 2D PSCs,we investigated the hydrophobicity of 2D perovskite films,the degradation characterization of BA2MA3Pb4l13 films under three aging conditions including high temperature and high humidity,standard solar and ultraviolet radiation,and the device aging performance.The experimental results showed that the 2D perovskite films exhibited excellent heat and humidity resistance,but it would degrade substantially under continuous light irradiation.Consequently.2D PSCs remained stable in nitrogen atmosphere,but degraded more rapidly under ultraviolet irradiation in contrast to the case of humidity and heat.Notably,the innovation in this dissertation lies in the following aspects:I.the pioneering usage of the novel in-situ tests based on KPFM for investigating the charge carrier transport mechanisms of 2D PSCs;2.the demonstration of the effect of PCBM modification craft in improving the performance of devices;3.the discovery of the stability differences of 2D PSCs,especially their instability under illumination.