Abstract Substitutional heterovalent doping has been considered as an effective method to control optical properties of lanthanide doped phosphors in the past, but it focuses only on three-dimensional and insulating crystal hosts. This study aimed to report the efficient upconversion enhancement of Er3+ induced by a new strategy of Ca2+ heterovalent doping in the layered semiconducting host based on BiOCl crystals concentrated by van der Waals force. The surface photovoltage (SPV) tests, theoretical calculations and optical probing effect of Eu3+ ions provided evidence that the replacement of Bi3+ with Ca2+ strengthened the macroscopic polarization and the corresponding spontaneous internal electric field (IEF) along the [001] of the BiOCl crystal sheet. The upconversion (UC) red and green emission intensities of the sample co-doped with 10 mol% Ca2+ ions were enhanced 39 and 12 times, respectively, compared with those of the Ca2+-free sample. Moreover, this study showed that the higher separation efficiency of photocarriers led to the prolongation of the decay time of excited energy levels under the strengthened intrinsic IEF by Ca2+-heterovalent doping, which was partially responsible for the UC photoluminescence (PL) enhancement of Er3+. This work not only provided new insight into the method for the engineering of UC emissions but also enhanced the understanding of layered semiconducting materials to modify the transition of lanthanide ions.

中文翻译：

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一种不同寻常的 Ca2+ 异价掺杂策略能够增强氯氧化铋层状半导体晶体中 Er3+ 的上转换

摘要 取代异价掺杂过去被认为是控制镧系元素掺杂荧光粉光学性能的有效方法，但它只关注三维和绝缘晶体基质。本研究旨在报告通过在基于范德华力浓缩的 BiOCl 晶体的层状半导体主体中 Ca2+ 异价掺杂的新策略诱导 Er3+ 的有效上转换增强。Eu3+ 离子的表面光电压 (SPV) 测试、理论计算和光学探测效应提供证据表明，用 Ca2+ 替代 Bi3+ 加强了沿 BiOCl 晶体片 [001] 的宏观极化和相应的自发内电场 (IEF) . 与不含 Ca2+ 的样品相比，共掺杂 10 mol% Ca2+ 离子的样品的上转换 (UC) 红色和绿色发射强度分别提高了 39 倍和 12 倍。此外，该研究表明，在通过 Ca2+-异价掺杂增强的本征 IEF 下，光载流子的更高分离效率导致激发能级的衰减时间延长，这是 Er3+ UC 光致发光 (PL) 增强的部分原因。这项工作不仅为 UC 发射的工程方法提供了新的见解，而且增强了对层状半导体材料的理解，以改变镧系元素离子的跃迁。该研究表明，在通过 Ca2+-异价掺杂增强的本征 IEF 下，光载流子的更高分离效率导致激发能级的衰减时间延长，这是 Er3+ UC 光致发光 (PL) 增强的部分原因。这项工作不仅为 UC 发射的工程方法提供了新的见解，而且增强了对层状半导体材料的理解，以改变镧系元素离子的跃迁。该研究表明，在通过 Ca2+-异价掺杂增强的本征 IEF 下，光载流子的更高分离效率导致激发能级的衰减时间延长，这是 Er3+ UC 光致发光 (PL) 增强的部分原因。这项工作不仅为 UC 发射的工程方法提供了新的见解，而且增强了对层状半导体材料的理解，以改变镧系元素离子的跃迁。