Anion Exchange in Cesium Lead Halide Perovskite Nanocrystals and Thin Films Using Trimethylsilyl Halide Reagents
Anion Exchange in Cesium Lead Halide Perovskite Nanocrystals and Thin Films Using Trimethylsilyl Halide Reagents
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DOI：
10.1021/acs.chemmater.8b02100
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发表时间：
2018-08-14
影响因子：
8.6
通讯作者：
Gamelin, Daniel R.
中科院分区：
文献类型：
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作者：
Creutz, Sidney E.;Crites, Evan N.;Gamelin, Daniel R.
CsPbX 3（X= Cl，Br，I）胶体纳米晶体的优异光电性能和易于合成使其自2015年首次报道以来成为科学界关注的主题。CsPbX 3纳米晶体最吸引人的方面之一，除了它们的高发光效率之外，是它们广泛可调的发射波长。通过改变卤化物成分，可以获得整个可见光谱。具有不同卤化物组成的纳米晶体可以直接合成或通过合成后阴离子交换从单一起始组合物获得。3，4阴离子交换反应性不限于铯铅卤化物钙钛矿;类似的行为已经在一系列基于卤化物的纳米晶体中被观察和利用，包括混合有机-无机卤化铅钙钛矿（MAPbX 3，MA= CH 3 NH3+）、三元卤化铋（MA 3Bi 2X 9）、卤化铯锑（Cs3 Sb 2X 9）和六方晶系（Cs2 AgBiX 6）。5− 8阴离子交换似乎是金属卤化物化学中一个普遍而强大的特征。尽管卤化铅钙钛矿纳米晶体中的阴离子交换反应相对容易，但常见的方法可能会出现并发症。卤化物钙钛矿纳米晶体的结构不稳定性现在得到了充分的理解，并且已经证明，广泛的试剂、溶剂和表面活性剂可以引起微生物降解，例如转化为相关的相或化学计量（方案1）。例如，CsPbBr 3纳米晶体可以通过用包括过量油胺的表面活性剂处理而部分或完全转化为Cs4 PbBr 6纳米晶体。9另一方面，添加烷基溴化铵表面活性剂导致CsPb 2Br 5的形成。考虑到这些结果，一些最常用的阴离子交换试剂，烷基卤化铵和含表面活性剂的金属卤化物盐溶液，也有无意中导致卤化物基纳米晶体的某种程度的分解或不期望的转化的风险。此外，需要在阴离子交换后纯化样品以除去过量的试剂和反应副产物，这可能导致进一步的生物降解。这些问题在具有超过CsPbX 3的更复杂组成的材料（例如掺杂的纳米晶体）中加剧，其中暴露于过量配体或母体阳离子可引起不期望的掺杂剂损失。11在这里，我们描述了使用三甲基甲硅烷基卤化物（TMSX，X= Cl，Br，I）作为CsPbX 3纳米晶体中阴离子交换的有效试剂。我们最近介绍了使用TMSX阴离子交换试剂的卤化物纳米晶体，特别是elpastorite（双钙钛矿）。7值得注意的是，只有TMSBr和TMSI允许从它们的较轻卤化物同系物成功合成Cs2 AgBiBr 6和Cs2 AgBiI 6纳米晶体，而更常见的阴离子交换试剂导致纳米晶体部分分解成其他相。我们已经发现TMSX试剂在涉及一系列金属卤化物纳米晶体的阴离子交换反应中是广泛有用的，并且它们的使用在我们的实验室中通常已经取代了其他阴离子交换试剂。尽管这里没有讨论，我们还发现TMSX试剂可用于直接合成CsPbCl 3和CsPbBr 3纳米晶体（参见SI）。[12]这里的结果突出了TMSX作为阴离子交换试剂的一些关键优势。这些优点中最重要的是（i）它们对不希望的副反应的惰性，（ii）它们有利的热力学，这使得更重的卤化物几乎可以化学计量地掺入CsPbX 3纳米晶体中，以及（iii）它们的挥发性，这使得…
The excellent optoelectronic properties and facile synthesis of CsPbX3 (X= Cl, Br, I) colloidal nanocrystals have made them the subject of intense scientific interest since they were first reported in 2015. 1, 2 One of the most appealing aspects of CsPbX3 nanocrystals, beyond their high luminescence efficiencies, is their widely tunable emission wavelength. By changing the halide composition, the entirety of the visible spectrum can be accessed. Nanocrystals with different halide compositions can be synthesized directly or accessed through postsynthetic anion exchange from a single starting composition. 3, 4 Anion-exchange reactivity is not limited to the cesium lead halide perovskites; similar behavior has been observed and exploited in a range of halide-based nanocrystals including hybrid organic− inorganic lead halide perovskites (MAPbX3, MA= CH3NH3+), ternary bismuth halides (MA3Bi2X9), cesium antimony halides (Cs3Sb2X9), and elpasolites (Cs2AgBiX6). 5− 8 Anion exchange appears to be a ubiquitous and powerful feature of metal-halide nanocrystal chemistry. Despite the relative ease of anion-exchange reactions in lead halide perovskite nanocrystals, common methods can present complications. The structural lability of halide perovskite nanocrystals is now well-appreciated, and it has been demonstrated that a wide range of reagents, solvents, and surfactants can cause nanocrystal degradation, eg, conversion to related phases or stoichiometries (Scheme 1). For instance, CsPbBr3 nanocrystals can be converted partially or fully toCs4PbBr6 nanocrystals through treatment with surfactants including an excess of oleylamine. 9 On the other hand, addition of an alkylammonium bromide surfactant causes formation of CsPb2Br5. 10 Given these results, some of the most commonly used anion-exchange reagents, alkylammonium halides and surfactant-containing metal halide salt solutions, also risk inadvertently causing some degree of decomposition or undesired transformation of halide-based nanocrystals. Moreover, the need to purify samples after anion exchange to remove excess reagents and reaction byproducts can cause further nanocrystal degradation. These issues are exacerbated in materials with more complex compositions beyond CsPbX3, such as doped nanocrystals, where exposure to excess ligands or parent cations can cause undesired dopant loss. 11 Here, we describe the use of trimethylsilyl halides (TMSX, X= Cl, Br, I) as effective reagents for anion exchange in CsPbX3 nanocrystals. We recently introduced the use of TMSX anionexchange reagents for halide nanocrystals, specifically elpasolites (double-perovskites). 7 Notably, only TMSBr and TMSI allowed successful synthesis of Cs2AgBiBr6 and Cs2AgBiI6 nanocrystals from their lighter halide congeners, whereas more common anion-exchange reagents caused partial decomposition of the nanocrystals to other phases. We have since found TMSX reagents to be broadly useful in anionexchange reactions involving a range of metal halide nanocrystals, and their use has generally supplanted other anionexchange reagents in our laboratory. Although not discussed here, we have also found that TMSX reagents are useful for the direct synthesis of CsPbCl3 and CsPbBr3 nanocrystals (see SI). 12 The results presented here highlight some key advantages of TMSX as nanocrystal anion-exchange reagents. Foremost among these advantages are (i) their inertness toward undesired side reactions,(ii) their favorable thermodynamics, which allow nearly stoichiometric incorporation of heavier halides into CsPbX3 nanocrystals, and (iii) their volatility, which enables …