Polymer-Free Films of Inorganic Halide Perovskite Nanocrystals as UV-to-White Color-Conversion Layers in LEDs.
Polymer-Free Films of Inorganic Halide Perovskite Nanocrystals as UV-to-White Color-Conversion Layers in LEDs.
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DOI：
10.1021/acs.chemmater.6b00954
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发表时间：
2016-05-10
期刊：
影响因子：
--
通讯作者：
Manna L
中科院分区：
文献类型：
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作者：
Palazon F;Di Stasio F;Akkerman QA;Krahne R;Prato M;Manna L
（led）正在成为一般照明应用的主要技术。1,2在过去的几年里，各种白光led已经被证明使用，例如，有机分子（oled） 3−7或无机量子点（QDs）的不同组成。实现白光发射的一种常见方法是将近紫外或蓝色LED与下转换材料（如荧光粉）耦合。最近，量子点已被集成到led中，取代了传统的荧光粉，以精细地调整发射光谱。在不同的可用量子点中，卤化铅钙钛矿纳米晶体最近成为许多光电应用中非常有前途的候选者。11−15胶体钙钛矿纳米晶体可以合成和/或合成后转化，因此可以很容易地制备出在整个可见光谱中发射不同波长的样品，具有高的光致发光量子产率（PLQY）。这可以通过改变化学成分（例如通过阴离子交换）或形状（立方体、血小板、片、线）来实现。18−21此外，从大块钙钛矿薄膜，22−25混合钙钛矿聚合物薄膜，26以及纳米晶体薄膜27,28中观察到电致发光，从而产生了第一个钙钛矿基led。钙钛矿纳米晶体也被用作白色发光led的颜色转换材料。最近的报道使用了一种商用蓝色氮化镓LED，在其顶部放置了绿色溴化物基纳米晶体。29,30然后用传统的红色荧光粉或碘基钙钛矿量子点完成光谱。在后一种情况下，溴化物和碘化物基钙钛矿纳米晶体都嵌入到聚合物基质中，以防止自发的粒子间阴离子交换反应。最近的报告表明，钙钛矿纳米晶体的形状控制可以用来调整发射波长：例如，基于溴的纳米片中的量子限制将发射波长从绿色（“标准”纳米立方体约为515 nm）转变为蓝色。这就避免了对蓝光光源的需要。此外，我们最近已经证明，真空下的x射线照射可以抑制钙钛矿纳米晶体上的阴离子交换反应，从而无需将其嵌入聚合物基质中。31最终，“完全无机”的铯基钙钛矿被报道
(LEDs) are becoming the main technology for general lighting applications. 1, 2 In the last years, a variety of white-LEDs have been demonstrated employing, for example, organic molecules (OLEDs) 3− 7 or inorganic quantum dots (QDs) of different composition. 8 A common way of achieving a white-light emission is to couple a near-UV or blue LED with downconversion materials such as phosphors. 9 More recently, QDs have been incorporated into LEDs, replacing conventional phosphors to tune finely the emission spectrum. 10 Among the different available QDs, lead halide-based perovskite nanocrystals have recently emerged as very promising candidates for many optoelectronic applications. 11− 15 Colloidal perovskite nanocrystals can be synthesized and/or transformed postsynthesis, so that samples emitting at different wavelengths throughout the whole visible spectrum, with high photoluminescence quantum yield (PLQY), can be prepared easily. This can be achieved either by changing the chemical composition (by anion-exchange for example) 16, 17 or the shape (cubes, platelets, sheets, wires). 18− 21 Also, electroluminescence has been observed from bulk perovskite films, 22− 25 blended perovskite-in-polymer films, 26 as well as from nanocrystals-only films 27, 28 leading to the first perovskitebased LEDs.Perovskite nanocrystals have also been used as colorconversion materials for white-emitting LEDs. Recent reports use a commercial blue GaN LED on top of which greenemitting bromide-based nanocrystals are placed. 29, 30 The spectrum is then completed either with conventional red phosphors or with iodide-based perovskite QDs. 29, 30 In the latter case, both bromide-and iodide-based perovskite nanocrystals are embedded in a polymer matrix to prevent spontaneous interparticle anion-exchange reactions. Recent reports have shown that shape control over perovskite nanocrystals can be used to tune the emission wavelength: for example, quantum confinement in bromide-based nanoplatelets shifts the emission wavelength from green (around 515 nm for “standard” nanocubes) to blue. 18 This avoids the need for a blue-emitting source. Additionally, we have recently demonstrated that X-ray irradiation under vacuum inhibits anion-exchange reactions on perovskite nanocrystals, making it unnecessary to embed them in a polymer matrix. 31 Eventually,“fully inorganic” cesium-based perovskites are reported to be