Colloidal Synthesis of Strongly Fluorescent CsPbBr(3) Nanowires with Width Tunable down to the Quantum Confinement Regime.
Colloidal Synthesis of Strongly Fluorescent CsPbBr(3) Nanowires with Width Tunable down to the Quantum Confinement Regime.
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DOI：
10.1021/acs.chemmater.6b03081
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发表时间：
2016-09-27
期刊：
影响因子：
--
通讯作者：
Manna L
中科院分区：
文献类型：
--
作者：
Imran M;Di Stasio F;Dang Z;Canale C;Khan AH;Shamsi J;Brescia R;Prato M;Manna L
半导体纳米线 1 (NW) 作为多种应用的候选材料受到了广泛关注，例如光电子学、2−4 光伏、5 热电学、6 和传感。 7 一些研究已经解决了强量子限制纳米线的制造问题，例如由 SnO2 8 或镉硫族化物制成。 9 卤化铅钙钛矿作为光伏和光电子领域有前途的材料 10, 11 的迅速崛起最近再次将纳米线置于聚光灯下。例如，基于甲基铵卤化铅钙钛矿 (CH3NH3PbX3) 的纳米线，通过表面引发溶液生长制备，12 据报道具有低激光阈值和高品质因数，PLQY 接近 100%，并且在整个可见光范围内具有广泛的可调性。使用全无机 CsPbX3 纳米线也获得了类似的结果。 13 已针对混合 14 和全无机 15、16 钙钛矿纳米线提出了胶体方法。对于杂化卤化铅钙钛矿，CH3NH3PbBr3 NW的长度可以生长至900 nm，并且可以通过改变反应时间来调节其宽度，从而在较短的反应时间内形成蓝色发光的纳米线（因此受到强烈限制），并在较长的反应时间内形成绿色发光的纳米线（不受限制）。全无机铯基钙钛矿比其混合对应物 17 更不易因水分水解，因此更适合应用。然而，迄今为止开发的协议可以提供长达 5 μm 长度的导线，但不能提供强量子限制条件下的宽度。在这里，我们报告了一种 CsPbBr3 NW 的胶体合成，其宽度可调节至量子限制范围（几个晶胞厚度），使用烷基胺和短烷基羧酸的混合物作为生长介质，遵循标准无空气技术（详细信息参见支持信息 SI 的图 S1 和表 S1）。在我们最初的方案中（类似于Zhang等人的方案16），我们可以通过调节辛胺（OctAm）与油胺（OlAm）的比例以及改变反应时间（从30分钟到50分钟）来合成宽度为10−20 nm（因此无限制）的纳米线，见图S1a、S2和S3。正如我们最近所表明的，添加具有长烷基链的酸（油酸）与短链和长链胺结合会导致纳米片的形成（图 S4）。 18 如果使用较短的烷基链羧酸（辛酸 OctAc，或己酸 HexAc）代替油酸，则可以制备更薄的纳米线（图S5）。通过增加短酸的浓度超过胺配体（OctAm 和 OlAm）的浓度，纳米线的宽度可以从 10±1 调整到 3.4±0.5 nm，即低至强量子限制区域（表 S1 和图 S6）。我们甚至可以生长约 2.8 nm 厚的纳米线（参见表 S1 和图 S6f），但随着时间的推移它们太不稳定，因此没有进一步考虑。其他被发现对控制纳米线宽度至关重要的参数是温度和反应时间。对于非受限纳米线（宽度≥ 10 nm），120− 130 C 是生长的最佳温度范围。对于受限纳米线（宽度≤10 nm）的生长，相同的温度范围（或更高的温度）除了线之外还会产生各种副产物（包括立方体），而低于70℃，纳米线的生长要慢得多，这有助于改善尺寸单分散性，并基本上导致无副产物的纳米线（见图S7）。对于非受限和受限 NW 来说，最佳生长时间均为 50 分钟。增加反应时间导致纳米线聚集。明场透射电子显微镜 (BF …
Semiconductor nanowires 1 (NWs) have received consid-erable attention as candidates in a wide variety of applications, such as in optoelectronics, 2− 4 photovoltaics, 5 thermoelectrics, 6 and sensing. 7 Several studies have addressed the fabrication of strongly quantum confined NWs, for example made of SnO2 8 or cadmium chalcogenides. 9 The rapid emergence of lead halide perovskites as promising materials in photovoltaics and optoelectronics 10, 11 has recently placed NWs under the spotlight again. For example, NWs based on methylammonium lead halide perovskites (CH3NH3PbX3), prepared by a surface-initiated solution growth, 12 were reported to have low lasing thresholds and high quality factors, PLQYs close to 100% and broad tunability through the whole visible range. Similar results have been obtained also with fully inorganic CsPbX3 NWs. 13 Colloidal approaches have been proposed for both hybrid 14 and fully inorganic 15, 16 perovskite NWs. For hybrid lead halide perovskites, CH3NH3PbBr3 NWs could be grown up to 900 nm in length and their width could be tuned by varying the reaction time, such that blue emitting NWs (hence strongly confined) were formed at short reaction times, and green emitting ones (not-confined) at longer times. Fully inorganic Cs-based perovskites are less susceptible to hydrolysis from moisture than their hybrid counterparts, 17 and therefore are preferable for applications. However, protocols developed to date could deliver wires of up to 5 μm length, but not with width in the strong quantum confinement regime. Here, we report a colloidal synthesis of CsPbBr3 NWs with width that is tunable down to the quantum confinement regime (few-unit-cell thick), using a mixture of alkyl amines and a short alkyl carboxylic acid as growth medium, following standard airfree techniques (for details see Figure S1 and Table S1 of the Supporting Information, SI). In our initial scheme (similar to that of Zhang et al. 16), we could synthesize NWs with 10− 20 nm width (hence nonconfined) by regulating the ratio of octylamine (OctAm) to oleylamine (OlAm) and by varying the reaction time (from 30 to 50 min), see Figures S1a, S2 and S3. The addition of an acid with a long alkyl chain (oleic acid) combined with short and long chain amines led instead to the formation of nanosheets (Figure S4), as recently shown by us. 18 If, in lieu of oleic acid, a shorter alkyl chain carboxylic acid (octanoic acid OctAc, or hexanoic acid HexAc) was used, thinner NWs could be prepared (Figure S5). By increasing the concentration of the short acid over that of the amine ligands (OctAm and OlAm), the width of nanowires could be tuned from 10±1 to 3.4±0.5 nm, that is, down to the strong quantum confinement regime (Table S1 and Figure S6). We could even grow NWs that were around 2.8 nm thick (see Table S1 and Figure S6f), but they were too unstable over time and were not considered further. Other parameters that were found critical to control the width of the NWs were the temperature and the reaction time. For nonconfined nanowires (width≥ 10 nm), 120− 130 C was the optimal temperature range for growth. For the growth of confined NWs (width≤ 10 nm), the same temperature range (or higher temperature) yielded various byproducts (including cubes) in addition to wires, whereas below 70 C the NW growth was much slower, which helped to improve the size mono dispersity and led essentially to NWs free of byproducts (see Figure S7). The optimal time of growth was 50 min for both nonconfined and confined NWs. Increasing the reaction time resulted in aggregation of the NWs.Bright field transmission electron microscopy (BF …
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影响因子：
41.2
作者：
Zhu, Haiming;Fu, Yongping;Zhu, X-Y.
通讯作者：
Zhu, X-Y.
影响因子：
64.8
作者：
Hochbaum, Allon I.;Chen, Renkun;Yang, Peidong
通讯作者：
Yang, Peidong
影响因子：
10.8
作者：
Protesescu L;Yakunin S;Bodnarchuk MI;Krieg F;Caputo R;Hendon CH;Yang RX;Walsh A;Kovalenko MV
通讯作者：
Kovalenko MV
影响因子：
56.7
作者：
Zhang, Wei;Eperon, Giles E.;Snaith, Henry J.
通讯作者：
Snaith, Henry J.
DOI：
10.1073/pnas.1600789113
发表时间：
2016-02-23
影响因子：
11.1
作者：
Eaton, Samuel W.;Lai, Minliang;Yang, Peidong
通讯作者：
Yang, Peidong