Synthesis And Photoelectric Conversion Properties Of Perovskite Hybrids Based On Pseudohalide SCN~-

The organic-inorganic perovskite hybrids combined the advantages of inorganic materials and organic materials,exhibiting good optical absorption properties,high carrier mobility,widely sources of materials,easy to form film in solution,adjustable structure and so on,thus they have important applications in the field of optoelectronics.Especially,in recent years,perovskite solar cells who take them as the core materials,have gotten a rapid development,and its photoelectric conversion efficiency increased from 3.8%to 21.6%.And battery improve,like photoelectric conversion efficiency,stability are closely related to the research on the perovskite materials.This paper introduced a new organic-inorganic perovskite hybrid based on the pseudohalide SCN^-,which replaces I^-of CH₃NH₃PbI₃ with SCN^-,and surrounding this systems,it mainly divided into three parts as follows to make a study:1)the composition and structure of the hybrid powder;2)the preparation of high-quality hybrid film and its application in perovskite solar cells;3)the impact of SCN^-introduced conventional CH₃NH₃PbI₃-based perovskite solar cells.And the main findings are as follows:?1?A new hybrid-?CH₃NH₃?₂Pb?SCN?₂I₂,was succesfully obtained by solid phase grinding method,extraction method and rotary evaporation method.When the ratio of raw materials Pb?SCN?₂ and CH₃NH₃I was changed,like 1:1,1:1.5 and 1:2,the composition of the final product was not changed.While the ratio was 1:3,the final product was proved to be the mixture of CH₃NH₃PbI₃ and?CH₃NH₃?SCN.SEM images did not show the layered texture as the typical layered hybrids,which is consistent with the results showed in the XRD.TG-DSC analysis revealed that the hybrid began to decompose into PbI₂ and MASCN at 150°C.Uv-vis analysis showed that?CH₃NH₃?₂Pb?SCN?₂I₂ had a strong visible light absorption in the range of 400-800 nm.?2??CH₃NH₃?₂Pb?SCN?₂I₂ films were prepared by one-step spin coating method,and we studied the effects of different solvent,different heat treatment temperature and heat treatment time on the film quality.It was found that a high quality film was obtained when we select 99.9%THF as the solvent and heat treatment at 60?for 30min.Then we konwed the band gap of?CH₃NH₃?₂Pb?SCN?₂I₂ is about 2.1eV by Tauc mapping.Finally,we prepared?CH₃NH₃?₂Pb?SCN?₂I₂-based perovskite solar cells on different substrates?BL-TiO₂/FTO,Meso-TiO₂/BL-TiO₂/FTO and NR-TiO₂/BL-TiO₂/FTO?and them performed photoelectric conversion efficiency were 0.27%,0.49%,0.56%respectively.?3?With 0 wt%,5 wt%,10 wt%and 15 wt%Pb?SCN?₂ addictive were incorporated in the precursor solution of CH₃NH₃PbI₃,respectively.It was found that the introduction of SCN^-greatly improved the film quality and increased the grain size from the nanometer level to the micron level.XRD,SEM?EDS?and IR analysis indicated that PbI₂ was formed at the grain boundary,and S,in SCN^-form,was mainly enriched on the PbI₂ at grain boundary.The short-circuit current of the perovskite solar cells was increased due to the introduction of SCN^-,and when the incorporation amount was 10wt%,the photoelectric conversion efficiency improved from 14.42%of pure CH₃NH₃PbI₃ to 16.76%.This was due to the introduction of SCN^-greatly improved the quality of the perovskite films,as well as the existence of the appropriate amount of PbI₂.