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通过改变四正辛基溴化铵(TOABr)用量和Cs/Pb摩尔比, 在室温下采用一步单溶剂法成功制备出单斜相CsPbBr 3和六方相Cs 4PbBr 6两种相结构可调的钙钛矿纳米晶. 研究发现, 当TOABr浓度较低时(Cs/Pb/Br = 1∶1∶4), 体系中主要生成了单斜相的CsPbBr 3纳米立方块, 该立方块主要经历了快速成核、尺寸分布聚焦生长和Ostwald熟化生长3个阶段, 最终尺寸为(11.8 ± 1.6) nm. 随着TOABr用量的增加, Br –与Pb 2+结合形成[PbBr 3] –和少量的[PbBr 4] 2–络合物, 两种络合物相互竞争. 在成核期和生长早期体系中[PbBr 3] –占主导, 因而形成大量的CsPbBr 3纳米晶, 随着反应的进行, 体系中过量的Br –会与纳米晶中的Pb相互作用, 导致CsPbBr 3纳米晶部分转变为具有六边形形状的Cs 4PbBr 6纳米晶, 同时[PbBr 4] 2–络合物的存在使得Cs 4PbBr 6纳米晶继续长大, 最终形成以CsPbBr 3为发光中心的CsPbBr 3-Cs 4PbBr 6复合纳米晶. 只有当TOABr用量为0.32 mmol时所得的CsPbBr 3-Cs 4PbBr 6复合纳米晶其光学性能和稳定性表现最佳. 在此浓度下改变Cs/Pb摩尔比只影响CsPbBr 3纳米晶和Cs 4PbBr 6纳米晶在体系中的相对含量, 当Cs 4PbBr 6纳米晶含量较高时其荧光强度和稳定性相对较差. 该工作对低温可控合成高效稳定的铯铅卤钙钛矿纳米晶提供一定思路.
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关键词:
- CsPbBr3-Cs4PbBr6复合纳米晶/
- 原位研究/
- 相转变/
- 形成动力学
All-inorganic cesium lead halide perovskites have shown great potential applications in optoelectronic field due to their fascinating optical properties. Although perovskite materials have achieved great success in various fields, their inherent ionic properties and high dynamic surface properties have led to their poor stability, hindering their applications. The preparation of CsPbBr 3-Cs 4PbBr 6nanocrystals has proven to be an effective strategy to enhance their photoluminescence properties and stability. Herein, we report an easy synthesis of CsPbBr 3-Cs 4PbBr 6nanocrystals with a diphase structure at room temperature by using Cs-OA, Pb-OA and TOABr as precursors in toluene. It is found that the phase transformation and the relative composition between CsPbBr 3and Cs 4PbBr 6are dependent on the concentration of TOABr and the ratio of Cs/Pb. The in-situPL experiments reveal that the formation of ~12 nm CsPbBr 3nanocubes experiences the fast nucleation, the focusing growth of size-distribution in early growth stage and Ostwald ripening growth in the later stage at a TOABr concentration of 0.16 mmol. With the increase of concentration of TOABr or molar ratio of Cs/Pb > 1 (Cs/Pb < 1), [PbBr 4] 2–complex and [PbBr 3] –complex can coexist and compete with each other in toluene, and the CsPbBr 3nucleations dominate in the early stage, then CsPbBr 3-Cs 4PbBr 6nanocomposites are gradually formed on CsPbBr 3nucleations as photoluminescence centers due to the continuous generation of [PbBr 4] 2–complex between TOABr and Pb 2+. The relative composition of Cs 4PbBr 6in CsPbBr 3-Cs 4PbBr 6nanocomposites can be improved from 4% to 85% with the concentration of TOABr increasing or Cs/Pb < 1. The optimized CsPbBr 3-Cs 4PbBr 6composite nanocrystals possess high PLQY and stability. Our work provides an understanding of the mechanism of phase transformation in cesium lead halide perovskite materials.-
Keywords:
- CsPbBr3-Cs4PbBr6composite nanocrystals/
- in-situstudy/
- phase transformation/
- formation kinetic
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