Lead sulfide quantum dots (QDs) photodetectors have received wide attention due to the merits of low-cost manufacturing, tunable bandgap, and the compatibility with flexible substrates. Currently, the QDs photodetectors fabricated via ligand exchange approaches suffer from a large dark current, which affects the overall performance. Herein, a precisely controlled atomic scale composite oxide infiltration method is developed to modify the QDs films via atomic layer deposition (ALD). The oxide infiltration enhances the electron coupling between QDs, lifts the photocurrent through effective electron transfer, and passivates the surface traps. At the same time, in situ characterizations show that ALD precursors directionally insert with the surface ligands of the QDs; thus, during the ALD process, the organic ligands remain attached to the surface of PbS QDs. The existence of long chain organic ligands which have a longer delivery distance guarantees the ultralow dark current (0.07 nA under bias voltage of 10 V) and high detectivity. In addition, ZnO is introduced to fill the QDs films via ALD to form the Al₂O₃/ZnO composite structure. ZnO has a higher carrier mobility which further improves the efficiency of electron transfer and enhances the photocurrent while maintaining the ultralow dark current.

中文翻译：

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超低暗电流的原子尺度复合氧化物渗入量子点光电探测器。

硫化铅量子点（QDs）光电探测器由于其低成本制造，可调节的带隙以及与柔性基板的兼容性而受到广泛关注。当前，通过配体交换方法制造的QDs光电检测器遭受大的暗电流，这影响了整体性能。本文中，开发了一种精确控制的原子尺度复合氧化物渗透方法，以通过原子层沉积（ALD）来修饰QDs膜。氧化物的渗透增强了量子点之间的电子耦合，通过有效的电子转移提升了光电流，并钝化了表面陷阱。同时，就地表征表明，ALD前体与QD的表面配体定向插入。因此，在ALD过程中，有机配体保持附着在PbS QD表面。具有较长传递距离的长链有机配体的存在保证了超低暗电流（在10 V偏置电压下为0.07 nA）和高检测率。另外，通过ALD引入ZnO以填充QDs膜以形成Al ₂ O ₃ / ZnO复合结构。ZnO具有较高的载流子迁移率，可进一步提高电子转移效率并增强光电流，同时保持超低暗电流。