Fabrication Of Mesostructured Perovskite Solar Cells And Investigation On The Photovoltaic Performances

Organometal trihalide perovskite materials have gained much attention due to their excellent optical absorption characteristics,balanced carrier transport properties with long diffusion lengths,as well as the facile preparation methods and the low fabrication cost,which also make such materials having a good potential application in next-genreration solar cells with high photovoltaic performance.Based on these promising optical and physical properties,perovskite solar cells have becoming a rising star in the photovoltaic field,of which the power conversion efficiency（PCE）has exceeded 22%within six years.However,this kind of solar cells have not been fully commercialized yet.One of the main reasons is that the stability of these devices is still unsatisfied.This thesis mainly foucsed on the optimization of the interface between TiO₂/perovskite layes and manipulation of the composition of perovskite active layer.It is proposed to resolve both efficiency and air stability issues of perovskite solar cells by improving the charges transportation property and perovskite crystallization process.The specific contents of this thesis are as follows:In the first part of this work,reliable fabrication processes for mesostructured perovskite solar cells in open air atmosphere was deveopoed.By taking the full consideration of the environment humidity,temperature,solvent type and surface condition on substrates,a set of optimized parameters for the fabrication processes have been eventually determined,which have been demonstrated that is suitable for open air atmosphere conditions.Especially,the preparation of TiO₂ compact layer based on solution method has been detailedly explored.And the influence of the quality and thickness of TiO₂ compact thin film on the photovoltaic performances of the cells has also been systematically investigated.Next,based on the preparation of mixed-cation perovskite films,the influence of mixed-cation on the crystallization mechanism,related optical properties and air stability for perovskite films have been studied.Firstly,high-quality MA_xFA_1-xPbI₃（MA refers to methyammonium cation,FA refers to formamidinium cation）perovskite films have been realized in air atmosphere by solvent-assisted sequential two-step deposition.By precisely tuning the mixing ratio of MA⁺ and FA⁺,the bandgap of the materials has become adjustable in the range of 1.51～1.59 eV,leading to a extended spectral response to the near-infrared region for the perovskite active layer.Meanwhile,the light absorption efficiency is also enhanced.Finally,the MA_xFA_1-XPbI₃ perovskite films were applied to the mesostructured perovskite solar cells.The results demonstrated that MA_xFA_1-xPbI₃ based devices have much better photovoltaic performances than MAPbI₃ or FAPbI₃ in terms of both efficiency and air-stability.Especially,the unpackaged MA_0.1FA_0.9PbI₃ based devices show the best stability with almost no PCE decay for over 30 days in ambient at 20℃-25℃ with relative humidity about 20%～45%.