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Anisotropic shape of CsPbBr3 colloidal nanocrystals: from 1D to 2D confinement effects.
Nanoscale ( IF 5.8 ) Pub Date : 2020-09-07 , DOI: 10.1039/d0nr03901b Violette Steinmetz 1 , Julien Ramade , Laurent Legrand , Thierry Barisien , Frédérick Bernardot , Emmanuel Lhuillier , Mathieu Bernard , Maxime Vabre , Imen Saïdi , Amal Ghribi , Kaïs Boujdaria , Christophe Testelin , Maria Chamarro
Nanoscale ( IF 5.8 ) Pub Date : 2020-09-07 , DOI: 10.1039/d0nr03901b Violette Steinmetz 1 , Julien Ramade , Laurent Legrand , Thierry Barisien , Frédérick Bernardot , Emmanuel Lhuillier , Mathieu Bernard , Maxime Vabre , Imen Saïdi , Amal Ghribi , Kaïs Boujdaria , Christophe Testelin , Maria Chamarro
Affiliation
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We synthesized strongly anisotropic CsPbBr3 nanocrystals with very narrow emission and absorption lines associated to confinement effects along one or two dimensions, called respectively nanoplatelets (NPLs) and nanosticks (NSTs). Transmission Electron Microscopy (TEM) images, absorption and photoluminescence (PL) spectra taken at low temperature are very precise tools to determine which kind of confinement has to be considered and to deduce the shape, the size and the thickness of nanocrystals under focus. We show that the energy of the band-edge absorption and PL peaks versus the inverse of the square of the NPL thickness has a linear behaviour from 11 monolayers (MLs) i.e. a thickness of 6.38 nm, until 4 MLs (2.32 nm) showing that self-energy correction compensates the increase of the exciton binding energy in thin NPLs as already observed in Cadmium chalcogenides-based NPLs. We also show that slight changes in the morphology of NSTs leads to a very drastic modification of their absorption spectra. Time-resolved PL of NSTs has a non-monotonous behaviour with temperature. At 5 K, a quasi-single exponential with a lifetime of 80 ps is obtained; at intermediate temperature, the decay is bi-exponential and at 150 K, a quasi-single exponential decay is recovered (≈0.4 ns). For NSTs, the exciton interaction with LO phonons governs the broadening of the absorption and PL peaks at room temperature and is stronger than in chalcogenides quantum dots and NPLs.
中文翻译：
CsPbBr3胶体纳米晶体的各向异性形状：从一维到二维约束效应。
我们合成了强各向异性CsPbBr 3纳米晶体，具有非常窄的发射线和吸收线，与一维或二维的约束效应相关，分别称为纳米片（NPL）和纳米棒（NST）。在低温下拍摄的透射电子显微镜（TEM）图像，吸收和光致发光（PL）光谱是非常精确的工具，可以确定必须考虑哪种限制并推断出焦点下的纳米晶体的形状，大小和厚度。我们表明，带边缘吸收峰和PL峰的能量与NPL厚度平方的倒数具有11个单层（ML）的线性关系，即厚度为6.38 nm，直到4 ML（2.32 nm）为止，这表明自能量校正可以补偿薄的NPL中激子结合能的增加，正如在基于硫属硫化物的NPL中已经观察到的那样。我们还表明，NSTs形态的微小变化会导致其吸收光谱发生非常剧烈的变化。NST的时间分辨PL具有随温度变化的非单调行为。在5 K时，获得了寿命为80 ps的准单指数。在中间温度下，衰减是双指数的，在150 K时，恢复了准单指数衰减（≈0.4ns）。对于NST，在室温下，与LO声子的激子相互作用决定了吸收峰和PL峰的加宽，并且比硫族化物量子点和NPL更强。
更新日期：2020-09-24
中文翻译：
CsPbBr3胶体纳米晶体的各向异性形状：从一维到二维约束效应。
我们合成了强各向异性CsPbBr 3纳米晶体，具有非常窄的发射线和吸收线，与一维或二维的约束效应相关，分别称为纳米片（NPL）和纳米棒（NST）。在低温下拍摄的透射电子显微镜（TEM）图像，吸收和光致发光（PL）光谱是非常精确的工具，可以确定必须考虑哪种限制并推断出焦点下的纳米晶体的形状，大小和厚度。我们表明，带边缘吸收峰和PL峰的能量与NPL厚度平方的倒数具有11个单层（ML）的线性关系，即厚度为6.38 nm，直到4 ML（2.32 nm）为止，这表明自能量校正可以补偿薄的NPL中激子结合能的增加，正如在基于硫属硫化物的NPL中已经观察到的那样。我们还表明，NSTs形态的微小变化会导致其吸收光谱发生非常剧烈的变化。NST的时间分辨PL具有随温度变化的非单调行为。在5 K时，获得了寿命为80 ps的准单指数。在中间温度下，衰减是双指数的，在150 K时，恢复了准单指数衰减（≈0.4ns）。对于NST，在室温下，与LO声子的激子相互作用决定了吸收峰和PL峰的加宽，并且比硫族化物量子点和NPL更强。
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