论文标题
CS2AG（SBXBI1-X）混合合金中的带隙降低BR6双钙钛矿薄膜
Bandgap Lowering in Mixed Alloys of Cs2Ag(SbxBi1-x)Br6 Double Perovskite Thin Films
论文作者
论文摘要
卤化双钙钛矿由于其低毒性元素的组成，空气稳定性和长电荷载体寿命而引起了极大的关注。但是，包括CS2Agbibr6在内的大多数双重钙钛矿都具有宽带的带盖，这限制了照片转换效率。可以通过使用SB3+来减少带隙，但是由于CS2AGSBBR6的高层能量，富含SB的合金很难合成，该cs2agsbbr6本身具有较宽的带隙。我们开发了一种基于溶液的途径，用于合成相纯CS2AG（SBXBI1-X）BR6薄膜，混合参数X连续在整个组合物范围内变化。我们透露，混合合金（x在0.5和0.9之间）表现出比纯SB-（2.18 eV）和基于BI的（2.25 eV）化合物的带镜（低至2.08 eV），并且与Vegard的定律有强偏差。通过深入的计算，我们提出降低带隙降低是由CS2AGBIBR6和CS2AGSBBR6之间的II型带对齐。 BI和SB S和P原子轨道之间的能量不匹配，再加上其非线性混合，导致合金采用比纯化合物更小的带隙。我们的工作证明了一种实现带隙减少的方法，并突出显示，通过将形成II型带对齐的材料配对在一起，可以在其他双钙钛合金合金中找到带隙弓。
Halide double perovskites have gained significant attention, owing to their composition of low-toxicity elements, stability in air and long charge-carrier lifetimes. However, most double perovskites, including Cs2AgBiBr6, have wide bandgaps, which limit photo conversion efficiencies. The bandgap can be reduced through hallowing with Sb3+, but Sb-rich alloys are difficult to synthesise due to the high formation energy of Cs2AgSbBr6, which itself has a wide bandgap. We develop a solution-based route to synthesis phase-pure Cs2Ag(SbxBi1-x)Br6 thin films, with the mixing parameter x continuous varying over the entire composition range. We reveal that the mixed alloys (x between 0.5 and 0.9) demonstrate smaller bandgaps (as low as 2.08 eV) than the pure Sb- (2.18 eV) and Bi-based (2.25 eV) compounds, with strong deviation from Vegard's law. Through in-depth computations, we propose that bandgap lowering arises from the Type II band alignment between Cs2AgBiBr6 and Cs2AgSbBr6. The energy mismatch between the Bi and Sb s and p atomic orbitals, coupled with their non-linear mixing, results in the alloys adopting a smaller bandgap than the pure compounds. Our work demonstrates an approach to achieve bandgap reduction and highlights that bandgap bowing may be found in other double perovskite alloys by pairing together materials forming a Type II band alignment.
