Preparation Process And Performance Optimization Of MAPbI₃ Absorption Layer For Perovskite Solar Cells

Perovskite solar cells with excellent photoelectric conversion efficiency,simple process and low preparation cost have attracted extensive attention of researchers.Perovskite absorber layer is the core component of perovskite solar cells.The morphology,grain size and distribution,pore content and distribution of perovskite layer are seriously affected by the preparation method,processing conditions and additives,which limit the photoelectric conversion performance of the cell devices.In this paper,the perovskite CH₃NH₃Pb I₃（MAPb I₃）single crystal was cultured,and the perovskite absorber layer was constructed on titanium oxide compact film by one-step solution deposition method and two-step sequential impregnation method,and the planar perovskite solar device was constructed.The effects of additives on the structure of perovskite absorber layer and the photoelectric properties of the cell devices were investigated by using u V-vis absorption spectrum,XRD,SEM,TEM and other characterization methods.The CH₃NH₃I（MAI）crystal was synthesized from methylamine aqueous solution and hydroiodic acid,and MAPb I₃precursor was prepared by mixed with lead iodide（Pb I₂）and MAI in theγ-butyrolactone solution.The tetragonal MAPb I₃perovskite single crystal with a diameter of about 3 mm was grown by inverse temperature gradient effect,and the morphology was complete.The stability of the single crystal was verified by one year of sealed storage.By using one-step solution deposition method on the surface of titanium oxide compact film,the comparative study found that the perovskite precursor solution was N,N-dimethylformamide（DMF）and dimethyl sulphoxide（DMSO）as the mixed solvent,and the perovskite absorber layer was uniform in grain size and compact.When using DMF and DMSO mixed solution with volume ratio of 4:1 to obtain perovskite absorber layer,the cell showed a better photoelectric conversion efficiency of 7.52%.It is found that in the process of perovskite precursor spin-coating,the selection of anti-solvent chlorobenzene drop time has a great influence on the film quality of perovskite absorber layer.By comparing different chlorobenzene addition time,it is found that when chlorobenzene drop time is 12 s,MAPb I₃layer is dense and has high coverage rate,large and uniform grain size,and corresponding perovskite solar cell device can obtain high photoelectric conversion efficiency.In the two-step sequential impregnation test,Pb I₂solution（DMF and DMSO mixed）of a small amount of 4-tert-butyl pyridine（TBP）was spin-coated on the surface of titanium oxide tight film to prepare the mesoporous Pb I₂layer.Then,the impregnation concentration and impregnation time of the isopropyl alcohol solution of MAI were compared.It was found that when MAI solution concentration was 10mg/m L and impregnation time was 10 min,the perovskite absorber layer with uniform grain size,compact arrangement and no pinhole structure was obtained,and the assembled cell achieved a better photoelectric conversion efficiency of 9.98%.