Near-infrared (NIR) emitting materials find a variety of applications in photodynamic therapy, national security, food inspection, and bioimaging, but achieving efficient NIR luminescence in lead-free perovskite materials is still challenging. Herein, we synthesized a series of lead-free Mo⁴⁺ alloyed Cs₂ZrCl₆ vacancy-ordered double perovskites with different Mo concentrations. These materials display tunable dual luminescence bands due to intrinsic host emission in the blue region and dopant induced d–d transitions emitting in the NIR region. Host- and dopant-induced emission can be excited at different energies, as revealed by spectroscopic studies. Minimum interaction between the host and dopant octahedra accounts for the dual emission in these 0D materials, further confirmed by density functional theory (DFT) calculations. Alloying Mo⁴⁺ reduces the band gap of these materials and DFT calculations confirm that the decrease in band gap is due to the increased contribution of Mo 4d states at the conduction band minima. Moreover, the structural stability of the host material also increases after Mo⁴⁺ alloying. Our study explored the tunable dual band emission in visible and NIR regions and enhanced structural stability in Mo⁴⁺ alloyed Cs₂ZrCl₆, thereby opening new avenues in the development of Pb-free NIR-emitting phosphors.

中文翻译：

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Cs2Zr1–xMoxCl6 的广泛双发射：增强无铅空位有序双钙钛矿的近红外发射


近红外（NIR）发射材料在光动力治疗、国家安全、食品检验和生物成像等领域有着广泛的应用，但在无铅钙钛矿材料中实现高效的近红外发光仍然具有挑战性。在此，我们合成了一系列不同Mo浓度的无铅Mo ⁴⁺ 合金Cs ₂ ZrCl ₆ 空位有序双钙钛矿。由于蓝色区域的本征主体发射和近红外区域的掺杂剂诱导的 d-d 跃迁发射，这些材料显示出可调谐的双发光带。正如光谱研究所揭示的那样，主体和掺杂剂诱导的发射可以在不同的能量下被激发。主体和掺杂剂八面体之间的最小相互作用解释了这些 0D 材料的双重发射，密度泛函理论 (DFT) 计算进一步证实了这一点。合金化 Mo ⁴⁺ 降低了这些材料的带隙，DFT 计算证实带隙的减小是由于 Mo 4d 态在导带最小值处的贡献增加所致。此外，Mo ⁴⁺ 合金化后，主体材料的结构稳定性也有所提高。我们的研究探索了可见光和近红外区域的可调谐双波段发射，并增强了 Mo ⁴⁺ 合金 Cs ₂ ZrCl ₆ 的结构稳定性，从而开辟了新的途径开发无铅近红外荧光粉。