通过卤化物合金化调节Cs3Bi2(Br1-xIx)9半导体的激子性质和电荷载流子动力学
Tuning Excitonic Properties and Charge Carrier Dynamics by Halide Alloying in Cs3Bi2(Br1-xIx)9 semiconductors
AI总结：
通过卤化物合金化调节Cs3Bi2(Br1-xIx)9半导体的激子性质和电荷载流子动力学，优化其光吸收和电荷传输性能。
摘要：
基于钙钛矿的铋卤化物半导体Cs3Bi2Br9被广泛研究作为光转换应用的光活性材料。然而，电荷生成和分离受到其较低的太阳光吸收和强激子结合能的限制。在这里，我们证明通过机械化学合成Cs3Bi2(Br1-xIx)9，通过控制Br与I的取代，可以改善光吸收和激子解离。X射线衍射和拉曼分析证实了原子水平的卤化物混合，并揭示了近x=0.8处的晶体学相变。从对薄膜的吸收测量中，我们确定了几种Cs3Bi2(Br1-xIx)9组分的吸收系数、乌巴赫尾和激子结合能。从这里，我们发现带隙可以从2.59 eV调节到1.93 eV（对于x=0.9），而激子结合能在x=0.6时达到最小值。最后，瞬态吸收光谱测量表明，重组寿命与乌巴赫能量之间存在弱相关性，其中寿命最长的材料具有最低的无序度。这些结果为设计具有有利光吸收特性和电荷载流子动力学的稳定铋卤化物半导体提供了有价值的见解。
英文摘要：
The perovskite-inspired bismuth halide semiconductor Cs3Bi2Br9 is widely investigated as photoactive material for light-conversion applications. However, charge generation and separation are inherently limited by its modest sunlight absorption and strong exciton binding energy, respectively. Here, we demonstrate that both the light absorption and exciton dissociation are improved by controlled substitution of Br with I via mechanochemical synthesis of Cs3Bi2(Br1-xIx)9. X-ray diffraction and Raman analyses confirm atomic-level halide mixing and reveal a crystallographic phase transition near x = 0.8. From absorption measurements on thin films, we determine the absorption coefficient, Urbach tail, and exciton binding energy for several Cs3Bi2(Br1-xIx)9 compositions. From here, we find that the band gap can be tuned from 2.59 to 1.93 eV (for x = 0.9), while exciton binding energies reach a minimum at x = 0.6. Finally, transient absorption spectroscopy measurements suggest a weak correlation between recombination lifetime and Urbach energy, where the longest lifetimes are observed for the materials with lowest disorder. These results offer valuable insights for designing stable bismuth halide semiconductors with favorable light absorption properties and charge carrier dynamics.
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