Szeremeta Janusz, Antoniak Magda A, Wawrzyńczyk Dominika, Nyk Marcin, Samoć Marek
Advanced Materials Engineering and Modelling Group, Wrocław University of Science and Technology, 50-370 Wrocław, Poland.
Saule Technologies, Wrocław Technology Park, Duńska 11, 54-427 Wrocław, Poland.
Nanomaterials (Basel). 2020 May 30;10(6):1054. doi: 10.3390/nano10061054.
The CsPbX nanocrystals (NCs) with X = I, Br, Cl, or the mixture of Br:I and Br:Cl in a 1:1 ratio were synthesized and characterized by TEM, DLS, and XRD. Recrystallization of the small luminescent NCs in the metastable cubic phase into bigger orthorhombic nanocrystals was monitored by XRD and identified as the main cause of the nanocolloid coagulation. The recrystallization also leads to a decrease in the photoluminescence quantum yield (QY) of the colloidal solution and shortening of the emission lifetime. The two-photon absorption cross-section σ values calculated from femtosecond Z-scan measurements were compared with those obtained based on the two-photon excited emission technique. These two techniques were shown to be equivalent with the cross-section values calculated per molar mass of CsPbX perovskite being in the range of 10-200 GM depending on the halide anions X. The σ values recalculated for the mole of the NCs were in the range of 10-10 GM, which is in good agreement with values previously reported elsewhere and the σ/M parameter was in the range of 0.01 to 0.33. This study shows the perovskite NCs to be a good nonlinear material with the third-order nonlinear optical susceptibility χ of the NCs on the order of 10 esu.
合成了X分别为I、Br、Cl或Br:I和Br:Cl 1:1比例混合物的CsPbX纳米晶体（NCs），并通过透射电子显微镜（TEM）、动态光散射（DLS）和X射线衍射（XRD）对其进行了表征。通过XRD监测了亚稳立方相中小的发光NCs重结晶为更大的正交晶系纳米晶体的过程，并确定这是纳米胶体凝聚的主要原因。重结晶还导致胶体溶液的光致发光量子产率（QY）降低以及发射寿命缩短。将飞秒Z扫描测量计算得到的双光子吸收截面σ值与基于双光子激发发射技术获得的值进行了比较。结果表明，这两种技术是等效的，根据卤化物阴离子X的不同，每摩尔CsPbX钙钛矿计算得到的截面值在10 - 200 GM范围内。针对NCs的摩尔数重新计算的σ值在10 - 10 GM范围内，这与其他地方先前报道的值高度一致，且σ/M参数在0.01至0.33范围内。本研究表明钙钛矿NCs是一种良好的非线性材料，其NCs的三阶非线性光学极化率χ约为10 esu。
