Study On The Performance And Stability Of Perovskite Solar Cells

Developing "green new energy" has been one of the hot topics in today's society.Solar energy,as a renewable energy source,has been playing an important role,so photovoltaic technology has attracted more and more researchers' attention.Perovskite solar cells as the third generation of solar cells have been widely concerned.Organic-inorganic hybrid perovskite solar cells(OIHP)have been one of the key concerns of researchers due to their excellent photoelectric characteristics.It has been reported that OIHP's efficiency has exceeded 25%,and its efficiency is comparable to that of silicon cells that have been commercialized.In order to fundamentally solve the problem of poor stability of perovskite solar cells(PSC),the organic cations in OIHP were all replaced with inorganic cations to form a pure inorganic perovskite solar cells.Among all the lead-based inorganic halide perovskites studied,CsPbX3(X=I,Br)has excellent thermal stability and excellent photoelectric characteristics,which provide a possible solution for the preparation of stable perovskite solar cells.However,the ratio of halogen elements in CsPbX3 material can not only determine the light absorption characteristics but also determine the structural stability of the material.The higher the proportion of element I,the smaller the bandgap of the material,the better the light absorption,the better the photoelectric characteristics,but the worse the resulting stability.In order to balance light absorption and structural stability,CsPbI2Br is chosen as the focus of this thesis.The main contents of this thesis are as follows:(1)Optimize the deposition thickness of CsPbI2Br film and improve the stability and quality of inorganic film.Polymer chains were introduced by doping the CsPbI2Br precursor solution with polyethylene glycol(PEG).Adding PEG to perovskite precursor solution can increase the viscosity of perovskite solution.Finally,by optimizing the content and molecular weight of PEG,the CsPbI2Br film was increased from 300nm to 450nm.In addition,during the crystallization process of PM-CsPbI2Br film,the polymer will be separated from perovskite phase and exist as a polymer matrix around each perovskite grain.In this way,PEG forms an organic network to protect PM-CsPbI2Br film,so that the photovoltaic device shows excellent stability.In addition,PEG formed an organic network that blocked the flow of liquid,prevented the agglomeration of precursor solution,increased the number of seed and increased the film coverage.Finally,FTO/compact TiO2/mesoporous TiO2/PM-CsPbI2Br/Spiro-MeOTAD/Au structure was adopted to prepare the device with a high repeatability of 12.9%,and the device maintained 90%of its initial solar cells efficiency after 4 months of storage under environmental conditions.(2)In this thesis,the morphology of inorganic CsPbI2Br perovskite thin film is improved by hot casting method,so as to reduce the holes and defects of the thin film and improve the quality of the thin film.This method aims at the problem of large and uneven distribution of thin film grains caused by fast crystallization of inorganic perovskite and less seed crystals in the traditional method.The interface temperature is increased by preheating the substrate,and the higher interface temperature is used to locally accelerate solvent volatilization to promote the generation of seed crystals at the interface of perovskite.At the same time,the temperature of the precursors is kept constant,and the rate of solvent evaporation and film crystallization is slowed down.Thus,the perovskite grains with smaller size,larger quantity and uniform distribution were obtained.By optimizing the process,The efficiency of CsPbI2Br solar cells with mesoporous structure is 10.1%and showed excellent stability.(3)In this thesis,A small amount of BA+ion was doped to the A site and 2D/3D mixed structure was used to optimize the film morphology and improve the film stability.Meanwhile,BA+ is a large-size ion,which can stabilize the material structure and further improve the material stability.By optimizing the content of BA+,we finally optimized the content of BA+to 10%,at which point the inorganic film presented the best state,dense uniform and almost no holes,and the device also showed excellent stability.