Research On The Preparation And Photovoltaic Property Of CsMX₃ Inorganic Perovskite Thin Films

The inorganic perovskite solar cells?PSCs?CsMX₃?M = Pb,Sn;X = I,Br?,as a newcomer of the photovoltaic field,have received great attention owing to their excellent photovoltaic properties and super thermal stability,which shows high potential to solve the stability bottleneck of the traditional organic-inorganic hybrid PSCs.However,they still have some key issues to be solved,such as RT phase change,poor structural stability,and lack of fabrication technology for high-quality films.To solve these problems,a solvent engineering process via intermediate phase transition is innovatively developed in this dissertation,and high-quality CsPbI₃ films and efficient photovoltaic devices are successfully achieved under fully open-air conditions.Meanwhile,a novel halogen vapor anion-exchange route is designed to enhance the structural stability,and thus stable CsPb(IxBr_1-x)₃ PSCs are obtained.Finally,the brandnew Pb-free CsSnI₃ photovoltaic materials are also studied regarding to the toxicity of Pb.This dissertation mainly includes the following aspects:Firstly,study of the preparation and photovoltaic property of CsPbI₃ Films.Cs₄PbI₆ intermediate phase is formed after spin-coating the precursor solution,and then it transforms into ?-CsPbI₃ through an isopropanol?IPA?annealing process.As a result,the as-prepared ?-CsPbI₃ films are still stable in air for more than 72 h,and this finding is very helpful for the development of stable CsPbI₃ materials.On the basis of the stable films,we realize the open-air preparation of CsPbI₃ inorganic PSCs,with a power conversion efficiency?PCE?of 4.13%,and the steady-state PCE of 1.88%?initial 3.13%?.Secondly,study of the preparation and photovoltaic property of CsPbX₃?X=I,Br?.Cs₄PbI₆ precursor film is prepared by the above method.Then CsPbBr₃ films are prepared by Br₂-VASP method,and CsPb(IxBr_1-x)₃?0<x?1?films are also obtained by MAX-VASP method.As a result,CsPb(IxBr_1-x)₃ films shows an excellent stability when the I ratio is less than 0.5.After heated at 100? for 150 min,there is no change from the appearances of CsPb(I_0.5Br_0.5)₃ and CsPbBr₃ films.On the basis of the stable films,we realize the CsPbBr₃ and CsPb(I_0.5Br_0.5)₃ inorganic PSCs,with a power conversion efficiency?PCE?of 2.36%,2.67% respectively.This simple,controllable,and scalable VASP method is very promising to promote the applicaition of inorganic PSCs.Thirdly,study of the preparation and photovoltaic property of CsSnI₃.Solution method and melting process are both used to prepare CsSnI₃ powder.It is found that Cl-doped powder by solution process is more stable.However,both powders easily transform into non-perovskite Cs₂SnI₆ in air atmosphere.Then the solution-processed powder is compressed into target,and the compact,uniform and stable Cs₂SnI₆ films are obtained by pulse laser deposition?PLD?method.The optical characteristic of Cs₂SnI₆ films are also measured,showing an absorption edge of 930 nm and a strong PL intensity at 873.23 nm,which imply that Cs₂SnI₆ is a promising new photovoltaic materials.At last,the compact,stable ? phase CsSnI₃ films are successfully prepared by using CsI,and SnI2 mixture target doped with 10% amount of SnCl2.The as-prepared films exhibit a strong absorption in the visible light region,extending up to ⁹50 nm.As the films appear relatively strong metallic,it results that CsSnI₃ devices show diode effect only.