Nanocrystals have exhibited unique optoelectronic properties and demonstrated a wide range of applications in light-emitting devices, semiconductor devices and solar cell devices. However, previous studies usually deposit nanocrystal films on traditional rigid substrates, limiting their applications in large-scale, direct-deposited flexible device fabrication processes, such as roll-to-roll printing process. Here, we report a direct deposition method for lead sulfide (PbS) nanocrystal films on flexible polymer substrates. By adding triethanolamine-coordinated Pb precursors to the reaction system to enhance the adhesion to the substrate and controlling the precursor ratios, we obtained high-quality flexible PbS films. The film is composed of octahedral PbS nanocrystals with preferred (111) orientation. The optical band gap of the nanocrystal films can be tuned from 1.32 eV to 1.60 eV by adjusting the ratio of the precursors, and an ideal band gap of 1.4 eV for single-junction solar cells was also obtained when Pb to S ratio reaches 1.4:1. More importantly, the flexible PbS films exhibit high charge carrier mobility of up to 25 cm² V−1 s−1, which is comparable to that of PbS films grown on traditional rigid substrates (e.g. silicon wafers or glasses). To our knowledge, this mobility is also the highest for PbS fabricated directly on flexible substrates. Our study provides a new approach for the preparation of low-cost and roll-to-roll processable nanocrystal films for future flexible optoelectronic devices.

中文翻译：

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在聚合物基板上直接沉积硫化铅纳米光电薄膜

纳米晶体表现出独特的光电特性，并在发光器件、半导体器件和太阳能电池器件中展示了广泛的应用。然而，先前的研究通常将纳米晶体薄膜沉积在传统的刚性基板上，限制了它们在大规模、直接沉积的柔性器件制造工艺中的应用，例如卷对卷印刷工艺。在这里，我们报告了一种在柔性聚合物基板上直接沉积硫化铅 (PbS) 纳米晶体薄膜的方法。通过在反应体系中添加三乙醇胺配位的 Pb 前驱体以增强对基材的附着力并控制前驱体的比例，我们获得了高质量的柔性 PbS 薄膜。该薄膜由具有优选（111）取向的八面体PbS纳米晶体组成。通过调整前驱体的比例，纳米晶薄膜的光学带隙可以从1.32 eV调整到1.60 eV，当Pb与S的比例达到1.4时，单结太阳能电池的理想带隙为1.4 eV： 1. 更重要的是，柔性 PbS 薄膜表现出高达 25 cm 的高载流子迁移率² 伏-1 s-1，这与在传统刚性基板（例如硅晶片或玻璃）上生长的 PbS 薄膜相当。据我们所知，这种迁移率对于直接在柔性基板上制造的 PbS 来说也是最高的。我们的研究为制备用于未来柔性光电器件的低成本和可卷对卷加工的纳米晶体薄膜提供了一种新方法。