Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: enabling photoelectrochemical characterization and electronic applications.
Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: enabling photoelectrochemical characterization and electronic applications.
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DOI：
10.1021/nn304563j
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发表时间：
2013-02-26
期刊：
影响因子：
17.1
通讯作者：
Brock, Stephanie L.
中科院分区：
文献类型：
--
作者：
Korala, Lasantha;Wang, Zhijie;Liu, Yi;Maldonado, Stephen;Brock, Stephanie L.
量子点薄膜的光电性能受到（1）界面化学差和（2）表面陷阱引起的非辐射复合的限制。为了解决这些性能问题，溶胶-凝胶方法被应用于制造薄膜的CdSe和核（壳）的CdSe（ZnS）量子点。高角度环形暗场扫描透射电子显微镜（HAADF-STEM）成像与化学分析证实，在溶胶-凝胶薄膜中的量子点的表面是硫属元素丰富，与氧化诱导的凝胶化机制，其中连接是通过形成颗粒之间的二硫属元素共价键实现的一致。通过热重、光谱和显微镜研究探讨了配体的去除和组装过程。通过温和的热退火进一步增强颗粒间的耦合，这去除了残留的配体并增强了QD连接性，导致具有上级电荷传输性质的QD溶胶-凝胶薄膜，如通过相对于由配体封端的QD组成的薄膜在白色光照射下电化学光电流的显著增强所示。一个超过2倍的光电流增强，并进一步增加光电压可以实现通过钝化的表面缺陷，通过与薄ZnS壳外涂层。调整界面和表面特征以优化光物理性质的能力表明，溶胶-凝胶方法可以形成适合一系列光电应用的量子点薄膜。
Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) non-radiative recombination due to surface traps. To address these performance issues, sol-gel methods are applied to fabricate thin films of CdSe and core(shell) CdSe(ZnS) QDs. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging with chemical analysis confirms that the surface of the QDs in the sol-gel thin films are chalcogen-rich, consistent with an oxidative-induced gelation mechanism in which connectivity is achieved by formation of dichalcogenide covalent linkages between particles. The ligand removal and assembly process is probed by thermogravimetric, spectroscopic and microscopic studies. Further enhancement of inter-particle coupling via mild thermal annealing, which removes residual ligands and reinforces QD connectivity, results in QD sol-gel thin films with superior charge transport properties, as shown by a dramatic enhancement of electrochemical photocurrent under white light illumination relative to thin films composed of ligand-capped QDs. A more than 2-fold enhancement in photocurrent, and a further increase in photovoltage can be achieved by passivation of surface defects via overcoating with a thin ZnS shell. The ability to tune interfacial and surface characteristics for the optimization of photophysical properties suggests that the sol-gel approach may enable formation of QD thin films suitable for a range of optoelectronic applications.
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影响因子：
17.1
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