Studies On Preparation And Properties Of Graphiticcarbon Nitride And Hybrid Perovskite Heterojunction

Graphitic carbon nitride?g-C₃N₄?has excellent thermal stability,good biocompatibility,non-toxic and environmental protection with only carbon and nitrogen,and other excellent performances,while showing the appropriate position of conduction band with the band gap?about 2.7 eV?,and is used as a good visible light-catalyzed semiconductor material.Protonated carbonitride?PCN?is capable of converting multilayer g-C₃N₄ into g-C₃N₄ sheets.Recently the perovskite solar cells with a simple process,low cost,high efficiency,has been rapid development just a few years.In this paper,rGO/g-C₃N₄,PCN/MAPbl3 and PCN/MAPbI3-xClx composites were synthesized using different methods.The photocatalytic degradation of organic pollutants was improved by modification of g-C₃N₄.CH3NH3PbI3?MAPbI3?and CH3NH3PbI3-xClx?MAPbI3-xClx?were modified by PCN to enhance the stability and photoelectric properties of perovskite.The study contents are mainly include as follow:?1?The graphene oxide?GO?was prepared by the Hummers method using graphite as precursors,and rGO was prepared via one-step hydrothermal method in the condition of high-temperature and high-pressure.The g-C₃N₄ was synthesized by thermal polymerization with melamine,and then ultrasonically mixed with different proportions of rGO to form aqueous solution.After that,the mixture solution was transferred into Teflon-lined stainless autoclave with hydrothermal reaction,forming two kinds of semiconductors co-doped composite catalyst.It was found that the photocatalytic degradation of methyl orange using rGO/g-C₃N₄ was 2.0 times higher than that of pure g-C₃N₄ and photoelectronic conversion efficiency was 1.4 times higher than that of pure g-C₃N₄.The decrease of fluorescence intensity indicates that rGO and g-C₃N₄ can form good catalyst,promote the migration rate of photogenerated carriers and enhance the photocatalytic activity of g-C₃N₄.?2?The flake g-C₃N₄ with light mass and easily floating was carried out by secondary high temperature calcination,and then PCN dissolved in concentrated hydrochloric acid was obtained by the synergistic effect of ultrasonic stripping and protonation of hydrochloric acid.The PCN/MAPbI3 perovskite light absorption layer was prepared by one-step solution method which have some advantages such as simple processes,the higher conversion of the precursor,and the easily preparation of mixed perovskite film.The PCN/MAPbI3 formed the nanocomposites heterojunction using one-step solution,and the transformation efficiency of the precursor has been effectively improved.This work found that PCN/MAPbI3 modified perovskite exhibited better photoelectric properties than pure MAPbI3,and the photoelectric conversion efficiency was 3.1%higher than that of pure MAPbI3?2.0%?.By changing the mass ratio of PCN and PbI2,The UV absorption spectrum intensity and the stability of the perovskite film can be further enhanced.?3?Based on the study of PCN/MAPbI3 perovskite film,PbCl₂ was introduced to prepare PCN/MAPbI3-xClx mixed perovskite by one-step solvent method.Since the perovskite film prepared by the traditional one-step process was poor,chlorobenzene was used as anti-solvent to enhance the quality of perovskite film.And the photoelectric properties and density of the prepared perovskite film was detected.The effects of perovskite films prepared by adding different ratios of PbCl2?mole percent relative to PbI2?on the visible light absorption capacity were also studied.The results show that the PCN/MAPbI3-xClx perovskite film prepared by adding 12%PbCl2 has stronger UV absorption intensity,and obtain a more flat and dense perovskite film with a larger particle size.And its photoelectric conversion efficiency is 4.8%higher than that of MAPbI3 with 2.0%,PCN/MAPbI3 with 3.1%and MAPbI3-xClx with 2.6%.XRD analysis showed that the addition of PbCl2 could promote the transformation of PbI2 and enhance the compactness and crystallization quality of perovskite membrane.PL rusults show the separation and transfer of the photogenerated carriers are promoted,so as to enhance the light absorption and photoelectric conversion efficiency.