Ferroelectric Properties Of Low Dimensional Lead Iodide Based Organic Perovskite

Now the fourth industrial revolution is to use information technology to promote industrial change,among which ferroelectric related technology is one of the foundations of information technology.After a hundred years of development,the research on traditional inorganic ferroelectrics has become mature.However,traditional ferroelectrics have some problems,such as difficult preparation,heavy metal pollution and so on.The research focus has turned to new hybrid organic-inorganic ferroelectrics,in which hybrid organic-inorganic lead-based perovskite(HOIP)materials have great potential in photovoltaic,optoelectronic and piezoelectric fields because of their rich physics It has attracted much attention due to its application.Methylamine lead iodide(MAPb I₃)is one of the most studied HOIP materials.It is found that the polarization characteristics of MAPb I₃ thin films contribute to the separation of photogenerated electron hole pairs in solar cells,and the bulk ferroelectric photovoltaic effect has a great influence on the photoelectric conversion efficiency of MAPb I₃ solar cells.MAPb I₃ has a band gap of 1.5-1.6e V,and good semiconductor conductivity,which inhibits ferroelectric behavior.Therefore,it is difficult to study ferroelectric behavior.The related work is rarely reported,and its ferroelectric behavior is controversial.In this paper,lead iodide based organic perovskite materials with low dimensional structure and ferroelectric behavior were obtained by adjusting the growth parameters during the growth of MAPb I₃.1.A novel lead iodide-based perovskite(DMA)₄Pb I₆ material with room temperature ferroelectricity was synthesized,and its spontaneous polarization is about 0.3?C/cm².(DMA)₄Pb I₆ undergoes a ferroelectric-ferroelectric phase transition at about 252k.Ferroelectric-ferroelectric phase transition is a first order phase transition,and the lag between heating and cooling is 18K.The temperature dependent dielectric properties of(DMA)₄Pb I₆ show that the dielectric properties of(DMA)₄Pb I₆ change with the phase transition point.The dielectric constant of(DMA)₄Pb I₆ at high temperature is about 1.3 times of that at low temperature.The absorption spectra show that(DMA)₄Pb I₆ is a direct band gap material with a band gap energy of 2.80e V.Blue emission centered at 2.7e V was observed in the experiment.In the(DMA)₄Pb X₆structure,the Pb X₆⁴⁺octahedron is completely decoupled by broadband DMA⁺molecules in all dimensions.The optical properties of(DMA)₄Pb I₆ crystal may be very similar to those of single Pb X₆⁴⁺cluster.We found that the ferroelectricity in 0d perovskite(DMA)₄Pb X₆ may help to adjust its optical and electrical properties.The unique photophysical properties of Pb I₆ based 0D perovskite have wide application prospects in the fields of optical pump and electric drive LED,laser,scintillator and so on.2.Synthesis of low temperature organic perovskite DMAPb I₃((CH₃)₂NH₂Pb I₃)ferroelectric crystal.Adding benzylamine to the solution is helpful to dissolve the crystals with high defect concentration and make them grow up.It is found that DMAPb I₃ has a full hysteresis loop below 260K,and the dielectric constant of DMAPb I₃ is more than 100 at different frequencies at room temperature.DMAPb I₃ is a one-dimensional perovskite structure material.Its Pb I₆ core is connected head to tail to form a unique one-dimensional chain structure.At the same time,we report the blue luminescence centered at 2.6e V.The ferroelectricity of DMAPb I₃ can be used to design more stable and efficient organic metal halide perovskite solar cells and optoelectronic devices.