Department of Chemistry and Applied Biosciences, Institute for Chemical and Bioengineering, ETH Zürich , Vladimir-Prelog-Weg 1, Zurich 8093, Switzerland.
Department of Chemistry and Applied Biosciences, Institute of Inorganic Chemistry, ETH Zürich , Vladimir-Prelog-Weg 1, Zurich 8093, Switzerland.
Nano Lett. 2018 Feb 14;18(2):1246-1252. doi: 10.1021/acs.nanolett.7b04838. Epub 2018 Jan 19.
Hybrid organic-inorganic perovskites and in particular formamidinium lead halide (FAPbX, X = Cl, Br, I) perovskite nanocrystals (NCs) have shown great promise for their implementation in optoelectronic devices. Specifically, the Br and I counterparts have shown unprecedented photoluminescence properties, including precise wavelength tuning (530-790 nm), narrow emission linewidths (<100 meV) and high photoluminescence quantum yields (70-90%). However, the controlled formation of blue emitting FAPb(ClBr) NCs lags behind their green and red counterparts and the mechanism of their formation remains unclear. Herein, we report the formation of FAPb(ClBr) NCs with stable emission between 440 and 520 nm in a fully automated droplet-based microfluidic reactor and subsequent reaction upscaling in conventional laboratory glassware. The thorough parametric screening allows for the elucidation of parametric zones (FA-to-Pb and Br-to-Cl molar ratios, temperature, and excess oleic acid) for the formation of nanoplatelets and/or NCs. In contrast to CsPb(ClBr) NCs, based on online parametric screening and offline structural characterization, we demonstrate that the controlled synthesis of Cl-rich perovskites (above 60 at% Cl) with stable emission remains a challenge due to fast segregation of halide ions.
杂化有机-无机钙钛矿，特别是甲脒铅卤（FAPbX，X = Cl、Br、I）钙钛矿纳米晶体（NCs），在光电设备中的应用具有广阔的前景。具体来说，Br 和 I 同系物表现出了前所未有的荧光性能，包括精确的波长调谐（530-790nm）、窄的发射线宽（<100meV）和高的荧光量子产率（70-90%）。然而，蓝色发射的 FAPb（ClBr）NCs 的可控形成落后于其绿色和红色同系物，其形成机制仍不清楚。在此，我们报告了在全自动液滴微流控反应器中形成发射波长在 440nm-520nm 之间的 FAPb（ClBr）NCs，随后在常规实验室玻璃器皿中进行反应放大。彻底的参数筛选有助于阐明纳米板和/或 NCs 形成的参数区（FA 与 Pb 和 Br 与 Cl 的摩尔比、温度和过量油酸）。与 CsPb（ClBr）NCs 相比，基于在线参数筛选和离线结构表征，我们证明了由于卤化物离子的快速分离，富 Cl 钙钛矿（Cl 含量高于 60at%）的可控合成具有稳定的发射，仍然是一个挑战。
