AI 中文总结
研究首次合成体相Cs2AgBiI6，通过阴离子交换制备微晶粉末，消除痕量水分是关键，还制备了薄膜。该成果展示了其在可见光范围的吸收及光载流子特性，实现了对这种难以捉摸的3D碘化物双钙钛矿的首次光电测量。
AI 中文摘要
三维（3D）碘化物双钙钛矿（铯榴石）半导体作为太阳能应用中潜在的无铅金属卤化物吸收层引起了人们的兴趣。尽管通过计算方法进行了广泛研究，但由于其预测的热力学不稳定性，它们在合成上仍然难以获得。本文报道了体相Cs2AgBiI6的首次合成，展示了微晶和薄膜形式。通过从纯相Cs2AgBiBr6微晶进行阴离子交换制备了Cs2AgBiI6微晶粉末。所得碘化物铯榴石在可见光范围内具有广泛吸收，光学带隙为1.70±0.05 eV，近红外光致发光中心为1.03 eV。我们确定消除体相Cs2AgBiBr6中的痕量水分是实现完全卤化物交换和分离具有相纯度的体相Cs2AgBiI6的关键因素。在惰性气氛中，微晶Cs2AgBiI6在室温下储存数月或加热至约70°C时不分解，在干燥空气中似乎同样稳定。基于这些见解，我们随后通过对Cs2AgBiBr6进行快速热蒸发然后进行阴离子交换，展示了制备纯相Cs2AgBiI6薄膜的方法。对这种Cs2AgBiI6薄膜的光电导测量证明了光载流子的产生和传输，这是对这种难以捉摸的3D碘化物双钙钛矿的首次光电测量。
英文摘要
Three-dimensional (3D) iodide double-perovskite (elpasolite) semiconductors have attracted interest as potential lead-free metal-halide absorber layers for solar applications. Although studied extensively by computational methods, they have remained largely inaccessible synthetically, consistent with their predicted thermodynamic instability. Here, we report the first synthesis of bulk Cs2AgBiI6, demonstrating both microcrystalline and thin-film forms. Microcrystalline powders of Cs2AgBiI6 were prepared via anion exchange from phase-pure Cs2AgBiBr6 microcrystals. The resulting iodide elpasolite shows broad absorption throughout the visible with a 1.70 +/- 0.05 eV optical bandgap and near-infrared photoluminescence centered at 1.03 eV. We identify the elimination of trace moisture in bulk Cs2AgBiBr6 as the critical factor enabling complete halide exchange and isolation of bulk Cs2AgBiI6 with phase purity. In inert atmosphere, microcrystalline Cs2AgBiI6 shows no decomposition when stored for months at room temperature or heated to ~70 °C, and it appears equally stable in dry air. Building upon these insights, we then demonstrate the preparation of phase-pure Cs2AgBiI6 films by flash thermal evaporation of Cs2AgBiBr6 followed by anion exchange. Photoconductivity measurements on such Cs2AgBiI6 films demonstrate photocarrier generation and transport, marking the first optoelectronic measurement on this elusive 3D iodide double perovskite.
Comments25 pages, 7 figures + TOC graphic, additional supporting information of 25 pages, 28 figures, 2 tables. Submitted to the Journal of the American Chemical Society (JACS)
