Ytterbium-doped halide double perovskites of the form Cs₂AgBX₆ (B = Bi, Sb, In and X = Cl, Br) are being explored as potential lead-free UV/blue to near-infrared (NIR) downconversion materials. Of the various B and X combinations, Cs₂AgSbBr₆ has only recently been synthesized and never yet deposited as a film using vapor deposition. Here, we report the deposition of undoped and Yb-doped Cs₂AgSbBr₆ thin films via thermal evaporation from CsBr, AgBr, SbBr₃, and YbBr₃. Film composition control is difficult due to the high volatility of SbBr₃. We explored various strategies, including co-evaporation and sequential deposition of layers, followed by postdeposition annealing. The formation of Cs₂AgSbBr₆ was confirmed with x-ray diffraction and optical absorption, although impurity phases such as Cs₂AgBr₃ were often present because the films easily became Sb-deficient due to volatile SbBr₃ leaving the film. NIR photoluminescence quantum yields of up to 12% were achieved with this material for the first time. The optical properties and reported bandgap transitions are critically reviewed and assessed in light of new optical absorption data from thin films. The Cs₂AgSbBr₆ film has an indirect bandgap at 1.95 ± 0.05 eV followed by a direct transition at 2.5 ± 0.05 eV.

中文翻译：

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Yb 掺杂 Cs2AgSbBr6 薄膜的物理气相沉积

_{Cs 2} AgBX ₆形式的掺镱卤化物双钙钛矿（B = Bi、Sb、In 和 X = Cl、Br）正在被探索作为潜在的无铅紫外/蓝光到近红外 (NIR) 下转换材料。在各种 B 和 X 组合中，Cs ₂ AgSbBr ₆最近才被合成，并且从未使用气相沉积沉积为薄膜。在这里，我们报告了通过 CsBr、AgBr、SbBr ₃和 YbBr _{3的热蒸发沉积未掺杂和 Yb 掺杂的 Cs 2} AgSbBr ₆薄膜。_{由于 SbBr 3}的高挥发性，薄膜成分控制困难. 我们探索了各种策略，包括层的共蒸发和顺序沉积，然后是沉积后退火。_{Cs 2} AgSbBr ₆的形成通过x射线衍射和光吸收得到证实，尽管杂质相如Cs ₂ AgBr ₃经常存在，因为由于挥发性SbBr ₃离开膜，膜很容易变得缺乏Sb。这种材料首次实现了高达 12% 的 NIR 光致发光量子产率。根据薄膜的新光学吸收数据，对光学特性和报告的带隙跃迁进行了严格审查和评估。Cs ₂ AgSbBr ₆薄膜具有 1.95 ± 0.05 eV 的间接带隙，然后是 2.5 ± 0.05 eV 的直接跃迁。