Solid-State Anion Exchange Reactions for Color Tuning of CsPbX3 Perovskite Nanocrystals
Solid-State Anion Exchange Reactions for Color Tuning of CsPbX3 Perovskite Nanocrystals
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DOI：
10.1021/acs.chemmater.6b03980
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发表时间：
2016-12-27
影响因子：
8.6
通讯作者：
Eychmuller, Alexander
中科院分区：
文献类型：
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作者：
Guhrenz, Chris;Benad, Albrecht;Eychmuller, Alexander
在此，我们报告了完全在固态下发生的高发射性全无机 CsPbBr3 纳米晶体 (NC) 的室温阴离子交换反应。通过将钙钛矿 NC 固定在纯卤化钾盐（KCl、KBr 和 KI）上，可以在几分钟到几小时内观察到从 Br 到 I 以及 Br 到混合 Br/Cl 的快速交换，无需施加额外的能量。通过调整嵌入盐基质的卤化物比例，CsPbX3（X = Cl、Br或I）NC的明亮荧光可以在较宽的光谱范围（400-700 nm）内调节，同时保持接近80%的初始光致发光量子产率和半高窄的全宽度。我们发现不同初始 CsPbX3 NC 和 KX 矩阵的组合会导致 NC 的最终卤素含量不同。这是通过主机晶格限制交换机制来解释的。通过在 2.2 GPa 的压力下压制软的、负载 NC 的盐可以加速阴离子交换速率。由于压制过程中钾盐的“冷流”行为，NC 可以完全嵌入透明盐粒中。该策略可以轻松调整 NC 负载以及所得复合材料的形状和厚度。用硅胶封装 NC 盐颗粒可确保嵌入式 NC 在环境条件下的坚固性和稳定性。易于处理和卓越的稳定性使得所得的钙钛矿复合材料对各种光子和光电应用具有吸引力，正如发光二极管的概念验证颜色转换层所证明的那样。
Herein, we report on a room-temperature anion exchange reaction of highly emitting, all-inorganic CsPbBr3 nanocrystals (NCs) taking place entirely in the solid state. A fast exchange from Br to I and Br to mixed Br/Cl without exertion of additional energy is observed within minutes to hours, taking place by immobilization of the perovskite NCs on pure potassium halide salts (KCl, KBr, and KI). Via adjustment of the halide ratios of the embedding salt matrix, the bright fluorescence of the CsPbX3 (X = Cl, Br, or I) NCs can be tuned over a wide spectral range (400-700 nm) while maintaining the initial photoluminescence quantum yields of similar to 80% and narrow full widths at half-maximum. We found that combinations of different initial CsPbX3 NCs and KX matrices result in different final halogen contents of the NCs. This is explained with a host-lattice limiting exchange mechanism. The anion exchange rate can be accelerated by pressing the soft, NC-loaded salts under pressure of 2.2 GPa. Because of the "cold flow" behavior of the potassium salts during the pressing, a complete embedding of the NCs into transparent salt pellets is achieved. This strategy allows for an easy adjustment of the NC loading as well as the form and thickness of the resulting composite. An encapsulation of the NC-salt pellets with silicone yields robustness and stability of the embedded NCs under ambient conditions. The ease of handling and the superior stability make the resulting perovskite composite materials attractive for various photonic and optoelectronic applications as demonstrated in a proof-of-concept color-converting layer for a light-emitting diode.