Controllable Preparation And Optical Properties Study Of Two-dimensional Sn-based Perovskite

Light-emitting diodes（LEDs）have been successfully applied to home lighting,outdoor lighting,and exhibition hall lighting because of their low power consumption,long life,high color purity,high shock resistance,small size,and non-pollution characteristics.Since the start of the 14th Five-Year Plan,many researchers have strengthened their exploration of new luminescent materials in order to achieve the new standard of"efficient green light-emitting"LEDs in the current context.At present,commercial white LED is mainly made by mixing phosphors of different colors（blue,green and red）and coating them on LED chips.However,the white LED prepared by this method is prone to the phenomenon of phosphor phase separation and reabsorption,resulting in the low light efficiency of LED.Therefore,it is of great significance to explore single-component white light materials.In recent years,organic-inorganic metal halide perovskite has become a new generation of luminescent materials recognized by the scientific research community.Due to its unique photoelectric properties,such as high fluorescence quantum efficiency,adjustable emission and low exciton binding energy.Among them,low-dimensional organic-inorganic hybrid perovskite is expected to become a new material for single-component white light.It shows strong self-trapped exciton luminescence,such as strong luminescence,large Stokes shift and wide spectrum emission.However,there are relatively few studies on the material synthesis,luminescence mechanism and device application of low-dimensional organic-inorganic hybrid perovskite.Based on this background,our project has carried out relevant research work around the synthesis of two-dimensional tin-based perovskite and its application in light-emitting diodes:the synthesis of two-dimensional tin-based perovskite and its application in LED:（1）Proposed a simple room temperature and recrystallization method and used it to prepare two-dimensional tin-based perovskite ODASn X_4.The reaction process can be completed quickly in one hour.In addition,the effects of hydrobromic acid concentration and hypophosphite concentration on the crystallization process and optical properties of ODASn X₄were discussed in detail.The ODASnBr₄ exhibits the strong emission centered at 586 nm,with the full width at half maxima of 180 nm,a large Stokes shift of more than 250 nm,a high quantum efficiency of 98.22%,and excellent thermal stability and environmental stability.In addition,the WLED packaged with ODASnBr₄ realizes adjustable relative color temperature and shows excellent luminous performance,with a CRI of 90.3.After the WLED works at 50m A for 3 hours,the light efficiency still remains the original 78.28%.This work provides a new idea for the synthesis of low-dimensional organic-inorganic hybrid perovskite materials.（2）Based on the research results in Chapter 2,synthesized two-dimensional tin-lead alloy perovskite ODAPb_xSn_1-xBr₄ by cooling recrystallization method.And discussed the influence of different tin-lead ratios on the morphology,structure and luminescent properties of ODAPb_xSn_1-xBr₄.The results show that the luminescence properties of ODAPb_xSn_1-xBr₄ can be adjusted by Sn-Pb alloying,and its luminescence properties are highly sensitive to lead content.By adjusting the proportion of perovskite B site,achieved three kinds of luminescence:monochromatic blue light,monochromatic yellow light and blue-yellow double peak emission.In addition,the relevant color temperature of the one-component WLED encapsulated by ODAPb_0.25Sn_0.75Br₄ perovskite is 4949 K,the color coordinates are（0.3459,0.3468）,and the light efficiency is 7.98 lm/W.This work shows that ODAPb_0.25Sn_0.75Br₄ tin-lead alloy perovskite has great commercial application potential in the field of single-component white light solid lighting.（3）Based on the previous two works,in order to further understand the properties of two-dimensional tin-lead alloy perovskite,constructed the crystal structure model of ODAPb_xSn_1-xBr₄（x=0,0.25,0.5,0.75,1）with 296 atoms by controlling the proportion of tin and lead.Through first-principles theoretical calculation,the effects of different tin-lead alloying on the energy band structure,density of states and electron density of two-dimensional ODAPb_xSn_1-xBr₄ perovskite were systematically studied.The results show that lead-rich perovskite is more susceptible to the spin-orbit coupling effect than pure tin perovskite.For all tin lead alloy perovskite structures in the middle proportion,the band gap is formed between the maximum value of the valence band of pure Sn and the minimum value of the conduction band of pure Pb,and leads to the band gap bending effect.In addition,found that the band gap bending effect of ODAPb_xSn_1-xBr₄ perovskite is the result of the combination of spin-orbit coupling effect and energy mismatch.To sum up,a new preparation strategy of two-dimensional organic-inorganic hybrid calcium ore proposed,studied the structure-activity relationship between the morphology and optical properties of two-dimensional tin-based calcium ore,and revealed the effect of different alloying degrees on the luminous properties and energy band structure of two-dimensional tin-lead alloy perovskite.One-component white LED devices are packaged based on tin-lead alloy perovskite,which provides a new idea for the application of low-dimensional organic-inorganic hybrid perovskite in optoelectronic field.