Underestimated Effect of a Polymer Matrix on the Light Emission of Single CsPbBr3 Nanocrystals
Underestimated Effect of a Polymer Matrix on the Light Emission of Single CsPbBr3 Nanocrystals
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DOI：
10.1021/acs.nanolett.9b00689
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发表时间：
2019-06-01
期刊：
影响因子：
10.8
通讯作者：
Kovalenko, Maksym V.
中科院分区：
文献类型：
--
作者：
Raino, Gabriele;Landuyt, Annelies;Kovalenko, Maksym V.
卤化铅钙钛矿APbX（3）（A = Cs或有机阳离子; X = Cl，Br，I）纳米晶体（NC）由于其作为经典和量子光源的特殊特性而成为激烈研究的主题。这类材料经常面临的许多挑战涉及长期光学稳定性，这是与APbX（3）化合物的不稳定和极性晶体结构相关的严重内在问题。当在单个颗粒水平进行光谱分析时，由于高度增强的污染物（例如，水分子、氧）超过NC比率，在通常使用的激发功率密度（1-100 W/cm（2））和环境条件下，NC光学性质的劣化在数十秒内发生。在这里，我们表明，选择一个合适的聚合物基质是至关重要的，从一个单一的NC获得稳定的光谱和抑制动态光致发光蓝移。特别是，聚苯乙烯（PS），最疏水的四个测试的聚合物，导致最好的光学稳定性，一至两个数量级高于聚（甲基丙烯酸甲酯），一种常见的聚合物封装含有极性酯基团。基于力场近似的分子力学模拟证实了PS在NC表面提供更致密的分子堆积的假设。这些发现强调了样品制备方法在单粒子水平上评估钙钛矿NCs光学特性时经常被忽视的作用，并指导了稳健单光子源的进一步设计。
Lead-halide perovskite APbX(3) (A = Cs or organic cation; X = Cl, Br, I) nanocrystals (NCs) are the subject of intense research due to their exceptional characteristics as both classical and quantum light sources. Many challenges often faced with this material class concern the long-term optical stability, a serious intrinsic issue connected with the labile and polar crystal structure of APbX(3) compounds. When conducting spectroscopy at a single particle level, due to the highly enhanced contaminants (e.g., water molecules, oxygen) over the NC ratio, deterioration of NC optical properties occurs within tens of seconds with typically used excitation power densities (1-100 W/cm(2)) and in ambient conditions. Here, we demonstrate that choosing a suitable polymer matrix is of paramount importance for obtaining stable spectra from a single NC and for suppressing the dynamic photoluminescence blueshift. In particular, polystyrene (PS), the most hydrophobic among four tested polymers, leads to the best optical stability, one to two orders of magnitude higher than that obtained with poly(methyl methacrylate), a common polymeric encapsulant containing polar ester groups. Molecular mechanics simulations based on a force-field approximation corroborate the hypothesis that PS affords for a denser molecular packing at the NC surface. These findings underscore the often-neglected role of the sample preparation methodologies for the assessment of the optical properties of perovskite NCs at a single-particle level and guide the further design of robust single photon sources.