| For the past few years,three-dimensional(3D)halide perovskite solar cells have been widely studied because of their excellent photovoltaic power generation characteristics and huge development prospects in the future,but the instability of the material itself has become an obstacle to industrialization.Therefore,the development of strategies to improve the stability of perovskite solar cells has become a research focus.Two-dimensional(2D)perovskite has proved to be a promising candidate material with its higher stability and easily regulated photoelectric properties.Traditional two-dimensional perovskite is a layered structure formed by introducing large organic spacer cations to break the co-top connection of lead halide octahedron in 3D perovskite.Although the introduction of hydrophobic cations can prevent or delay the direct contact between perovskite crystals and water,showing good humidity stability,it also leads to poor charge transfer between perovskite layers,and the cell efficiency is not very ideal.Therefore,the method of substituting X-site halogen ions with halogen-like halogens has been applied to prepare 2D perovskite materials.All-inorganic 2D Cs2Pb(SCN)2X2 perovskites have been shown to have smaller layer spacing than traditional cation-induced 2D perovskites and may have potential applications in optoelectronic devices.In this paper,2D Cs2Pb(SCN)2(I1-x Brx)2(x=0,1/4,1/2,3/4,1)series color perovskite solar cells were prepared by changing the ratio of iodine and bromine content at x site.With the increase of Br content in the system,the color of the film changed from red to yellow.Further adjustment of spin-coating parameters was carried out to improve the quality of the films and to characterize the optical and electrical properties of the films and devices.A number of test results have proved that Cs2Pb(SCN)2I2 perovskite devices have better photoelectric performance than other devices in the series.By adding phenyl trimethyl ammonium bromide(PTABr)layer between the light absorption layer and the hole transport layer on the basis of Cs2Pb(SCN)2I2 perovskite solar cells,the difficulty of poor diffusion of hole transport material spiro-OMeTAD on 2D perovskite films is overcome,and adverse direct contact between the two is avoided.Obviously improve the photoelectric conversion efficiency of the cells.Formamidine hydrochloride(FAC1)was added to 2D Cs2Pb(SCN)2I2 perovskite precursor solution.The results showed that FACl played a role in modulating crystallization,delaying the crystallization rate,making the grain size more uniform,effectively improving the carrier transport performance,and obtaining Cs2Pb(SCN)2I2 thin films with fewer defects.The 2D Cs2Pb(SCN)2I2 perovskite solar cells prepared on this basis show excellent photoelectric performance,and the champion efficiency is 4.7%,which is the highest efficiency of perovskite solar cells with bright red color reported so far.When the optimal device is stored in a nitrogen glove box for 800 h,the conversion efficiency decreases by about 20%,showing good stability.In addition,the effect of the introduction of phenyltrimethyl ammonium iodide(PTAI)between the light absorption layer and the hole transport layer on the Cs2Pb(SCN)2I2 perovskite solar cells was investigated.The results show that PTAI reacts with Pb(SCN)2 on the surface to generate a new two-dimensional substance to reduce defects,improve the level matching and optimize the performance of the device.Finally,Cs2Pb(SCN)2I2 perovskite cells achieve 5.12%photoelectric conversion efficiency,further updating the highest efficiency obtained in this study,which is the highest efficiency of this kind of cells at present. |
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