Empa-Swiss Federal Laboratories for Materials Science and Technology , Überlandstrasse 129, 8600, Dübendorf, Switzerland.
Nano Lett. 2016 Mar 9;16(3):1869-77. doi: 10.1021/acs.nanolett.5b04981. Epub 2016 Feb 4.
Prior to this work, fully inorganic nanocrystals of cesium lead halide perovskite (CsPbX3, X = Br, I, Cl and Cl/Br and Br/I mixed halide systems), exhibiting bright and tunable photoluminescence, have been synthesized using conventional batch (flask-based) reactions. Unfortunately, our understanding of the parameters governing the formation of these nanocrystals is still very limited due to extremely fast reaction kinetics and multiple variables involved in ion-metathesis-based synthesis of such multinary halide systems. Herein, we report the use of a droplet-based microfluidic platform for the synthesis of CsPbX3 nanocrystals. The combination of online photoluminescence and absorption measurements and the fast mixing of reagents within such a platform allows the rigorous and rapid mapping of the reaction parameters, including molar ratios of Cs, Pb, and halide precursors, reaction temperatures, and reaction times. This translates into enormous savings in reagent usage and screening times when compared to analogous batch synthetic approaches. The early-stage insight into the mechanism of nucleation of metal halide nanocrystals suggests similarities with multinary metal chalcogenide systems, albeit with much faster reaction kinetics in the case of halides. Furthermore, we show that microfluidics-optimized synthesis parameters are also directly transferrable to the conventional flask-based reaction.
在此项工作之前，使用传统批量（瓶式）反应，已成功合成出具有明亮可调荧光的全无机卤化铅钙钛矿（CsPbX3，X = Br，I，Cl 和 Cl/Br、Br/I 混合卤化物体系）的纳米晶体。不幸的是，由于离子交换合成此类多元卤化物体系涉及到非常快的反应动力学和多个变量，我们对控制这些纳米晶体形成的参数的理解仍然非常有限。在此，我们报告了使用基于液滴的微流控平台来合成 CsPbX3 纳米晶体。在这种平台上进行在线光致发光和吸收测量以及试剂的快速混合，使得可以严格快速地绘制反应参数图，包括 Cs、Pb 和卤化物前体的摩尔比、反应温度和反应时间。与类似的批量合成方法相比，这在试剂使用和筛选时间方面节省了大量成本。对金属卤化物纳米晶体成核机制的早期洞察表明，其与多元金属硫属化物体系具有相似性，尽管卤化物的反应动力学要快得多。此外，我们还表明，微流控优化的合成参数也可以直接转移到传统的瓶式反应中。
