Study On All-inorganic Cs₂PbI₂（SCN）₂ Perovskite Solar Cells

Thiocyanate anion perovskite has unique crystal structure and photoelectric properties,and its structural formula is A2PbI2(SCN)2 crystal is a typical two-dimensional perovskite material.When a is Cs,in the structure of Cs2PbI2(SCN)2,one Pb atom is surrounded by four iodine atoms and two SCN groups,and the halogen atom is shared by the two nearest Pb atoms.In recent years,layered perovskites with long chain cations at a site have been widely studied,while layered perovskites with anionic SCN have been less studied.With Cs2PbI2(SCN)2 Planar heterojunction solar cells with 2 as light absorbers have high photoelectric conversion efficiency in long-chain cationic two-dimensional perovskite devices.In addition to benefiting from SCN the ultra-small interlayer spacing of ions,it is also conducive to the charge transfer between layers.In addition,compared with the traditional cationic layered perovskite and three-dimensional perovskite,Cs2PbI2(SCN)2 is more stable has excellent photoelectric detection performance.Therefore,Cs2PbI2(SCN)2 has great potential in perovskite batteries and photodetectors.In this paper,the solution method was used to determine the concentration of CsI and Pb(SCN)2 the molar ratio is 2:1,A small amount of different chlorine containing additives,such as FACl,CsCl and MACl,were introduced into the precursor solution.The effect of cation size in different chlorine containing additives on battery performance was studied.The results show that,when using FACl as additive,FA ions can be reduced during vacuum annealing first enter into the lattice of perovskite,due to the linear SCN is larger,The size of cations inserted between octahedrons is more strictly limited by anions.With the prolongation of annealing time,FA+ions will be expelled out of octahedron and exist on the surface or grain boundary of perovskite films.FA+ ions and Cl-ions passivate the defects on the surface of perovskite films.At the same time,high quality Cs2PbI2(SCN)2 thin films were prepared because of the effect of FA+ ions.When a certain amount of FACl was used as additive,the cell showed the best photoelectric characteristics.On this basis,the wettability between the perovskite film and the hole transport material is effectively improved by spin coating ptabr solution on the surface of the perovskite film.At the same time.because PTA has good hydrophobicity.spin coating can effectively improve the humidity stability of the battery Finally,Cs2PbI2(SCN)2 perovskite battery can achieve 4.53%photoelectric conversion efficiency,which is the highest efficiency of this kind of battery.The short circuit current is 8.75 mA/cm2,the open circuit voltage is 0.89V,and the fill factor is 58.45%.In addition,when the optimal device is stored in nitrogen glove box for 30 days,the photoelectric conversion efficiency of the device is only decreased by about 18%,showing good stability.