Epps Robert W, Felton Kobi C, Coley Connor W, Abolhasani Milad
Chemical and Biomolecular Engineering, North Carolina State University.
Chemical Engineering, Massachusetts Institute of Technology.
J Vis Exp. 2018 May 10(135):57666. doi: 10.3791/57666.
Colloidal semiconductor nanocrystals, known as quantum dots (QDs), are a rapidly growing class of materials in commercial electronics, such as light emitting diodes (LEDs) and photovoltaics (PVs). Among this material group, inorganic/organic perovskites have demonstrated significant improvement and potential towards high-efficiency, low-cost PV fabrication due to their high charge carrier mobilities and lifetimes. Despite the opportunities for perovskite QDs in large-scale PV and LED applications, the lack of fundamental and comprehensive understanding of their growth pathways has inhibited their adaptation within continuous nanomanufacturing strategies. Traditional flask-based screening approaches are generally expensive, labor-intensive, and imprecise for effectively characterizing the broad parameter space and synthesis variety relevant to colloidal QD reactions. In this work, a fully autonomous microfluidic platform is developed to systematically study the large parameter space associated with the colloidal synthesis of nanocrystals in a continuous flow format. Through the application of a novel translating three-port flow cell and modular reactor extension units, the system may rapidly collect fluorescence and absorption spectra across reactor lengths ranging 3 - 196 cm. The adjustable reactor length not only decouples the residence time from the velocity-dependent mass transfer, it also substantially improves the sampling rates and chemical consumption due to the characterization of 40 unique spectra within a single equilibrated system. Sample rates may reach up to 30,000 unique spectra per day, and the conditions cover 4 orders of magnitude in residence times ranging 100 ms - 17 min. Further applications of this system would substantially improve the rate and precision of the material discovery and screening in future studies. Detailed within this report are the system materials and assembly protocols with a general description of the automated sampling software and offline data processing.
胶体半导体纳米晶体，即量子点（QDs），是商业电子产品中一类快速发展的材料，如发光二极管（LED）和光伏电池（PVs）。在这类材料中，无机/有机钙钛矿因其高电荷载流子迁移率和寿命，在高效、低成本的光伏电池制造方面展现出显著的进步和潜力。尽管钙钛矿量子点在大规模光伏和发光二极管应用中有机会，但对其生长途径缺乏基本和全面的了解，阻碍了它们在连续纳米制造策略中的应用。传统基于烧瓶的筛选方法通常成本高、劳动强度大，且在有效表征与胶体量子点反应相关的广泛参数空间和合成多样性方面不够精确。在这项工作中，开发了一个完全自主的微流控平台，以系统地研究与连续流形式的纳米晶体胶体合成相关的大参数空间。通过应用一种新型的平移三端口流动池和模块化反应器扩展单元，该系统可以在3 - 196厘米的反应器长度范围内快速收集荧光和吸收光谱。可调节的反应器长度不仅将停留时间与速度依赖的传质解耦，还由于在单个平衡系统中表征40个独特光谱，大大提高了采样率和化学消耗量。采样率可达每天30,000个独特光谱，条件涵盖停留时间在100毫秒 - 17分钟范围内的4个数量级。该系统的进一步应用将在未来研究中大幅提高材料发现和筛选的速度和精度。本报告详细介绍了系统材料和组装协议，并对自动采样软件和离线数据处理进行了一般描述。
