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首页> 外文期刊>ACS nano >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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Uniform thin films of CdSe and CdSe(ZnS) core(shell) quantum dots by sol-gel assembly: Enabling photoelectrochemical characterization and electronic applications

机译：通过溶胶-凝胶组装的CdSe和CdSe（ZnS）核（壳）量子点的均匀薄膜：实现光电化学表征和电子应用

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摘要

Optoelectronic properties of quantum dot (QD) films are limited by (1) poor interfacial chemistry and (2) nonradiative 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 interparticle 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.
机译：量子点（QD）薄膜的光电特性受到（1）不良的界面化学和（2）由于表面陷阱而引起的非辐射复合的限制。为了解决这些性能问题，溶胶-凝胶法被用于制造CdSe和核（壳）CdSe（ZnS）量子点的薄膜。具有化学分析的高角度环形暗场扫描透射电子显微镜（HAADF-STEM）成像证实，溶胶-凝胶薄膜中QD的表面富含硫属元素，这与氧化诱导的胶凝机制相符，其中连通性通过在颗粒之间形成二卤化二价共价键来实现。配体的去除和组装过程通过热重分析，光谱学和显微镜研究来探究。通过温和的热退火进一步增强粒子间耦合，从而消除残留的配体并增强QD连接性，从而使QD溶胶-凝胶薄膜具有优异的电荷传输性能，如白光照射下电化学光电流相对于薄膜的显着增强所显示由配体封端的量子点组成。通过使用薄的ZnS外壳进行覆盖来钝化表面缺陷，可以使光电流提高2倍以上，并进一步提高光电压。调整界面和表面特性以优化光物理性能的能力表明，溶胶-凝胶法可以形成适合于一系列光电应用的QD薄膜。

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