Epitaxial heterostructures of colloidal lead halide perovskite nanocrystals (NCs) with other semiconductors, especially the technologically important metal chalcogenides, can offer an unprecedented level of control in wavefunction design and exciton/charge carrier engineering. These NC heterostructures are ideal material platforms for efficient optoelectronics and other applications. Existing methods, however, can only yield heterostructures with random connections and distributions of the two components. The lack of epitaxial relation and uniform geometry hinders the structure–function correlation and impedes the electronic coupling at the heterointerface. This work reports the synthesis of uniform, epitaxially grown CsPbBr₃/CdS Janus NC heterostructures with ultrafast charge separation across the electronically coupled interface. Each Janus NC contains a CdS domain that grows exclusively on a single {220} facet of CsPbBr₃ NCs. Varying reaction parameters allows for precise control in the sizes of each domain and readily modulates the optical properties of Janus NCs. Transient absorption measurements and modeling results reveal a type II band alignment, where photoexcited electrons rapidly transfer (within ≈9 picoseconds) from CsPbBr₃ to CdS. The promoted charge separation and extraction in epitaxial Janus NCs leads to photoconductors with drastically improved (approximately three orders of magnitude) responsivity and detectivity, which is promising for ultrasensitive photodetection.

中文翻译：

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用于高效电荷分离的外延 CsPbBr3/CdS Janus 纳米晶异质结构

胶体卤化铅钙钛矿纳米晶体 (NC) 与其他半导体，尤其是技术上重要的金属硫族化物的外延异质结构，可以在波函数设计和激子/载流子工程中提供前所未有的控制水平。这些 NC 异质结构是高效光电子学和其他应用的理想材料平台。然而，现有方法只能产生具有随机连接和两个组件分布的异质结构。外延关系和均匀几何形状的缺乏阻碍了结构-功能相关性并阻碍了异质界面处的电子耦合。_{这项工作报告了均匀、外延生长的 CsPbBr 3}的合成/CdS Janus NC 异质结构，在电子耦合界面上具有超快电荷分离。_{每个 Janus NC 都包含一个 CdS 域，该域专门生长在 CsPbBr 3} NC的单个 {220} 面上。改变反应参数可以精确控制每个域的大小，并轻松调节 Janus NC 的光学特性。瞬态吸收测量和建模结果揭示了 II 型带排列，其中光激发电子快速（在 ≈9 皮秒内）从 CsPbBr ₃转移到 CdS。外延 Janus NCs 中促进的电荷分离和提取导致光电导体具有显着提高（大约三个数量级）的响应度和检测率，这有望用于超灵敏光电检测。