Chaudhary Madhusudan, Karmakar Abhoy, Mishra Vidyanshu, Bhattacharya Amit, Mumbaraddi Dundappa, Mar Arthur, Michaelis Vladimir K
Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
Commun Chem. 2023 Apr 19;6(1):75. doi: 10.1038/s42004-023-00874-w.
Aliovalent substitution of the B component in ABX metal halides has often been proposed to modify the band gap and thus the photovoltaic properties, but details about the resulting structure have remained largely unknown. Here, we examine these effects in Bi-substituted CsSnBr. Powder X-ray diffraction (XRD) and solid-state Sn, Cs and Bi nuclear magnetic resonance (NMR) spectroscopy were carried out to infer how Bi substitution changes the structure of these compounds. The cubic perovskite structure is preserved upon Bi-substitution, but with disorder in the B site occurring at the atomic level. Bi atoms are randomly distributed as they substitute for Sn atoms with no evidence of Bi segregation. The absorption edge in the optical spectra shifts from 1.8 to 1.2 eV upon Bi-substitution, maintaining a direct band gap according to electronic structure calculations. It is shown that Bi-substitution improves resistance to degradation by inhibiting the oxidation of Sn.
人们经常提出，在ABX金属卤化物中对B组分进行异价取代可以改变带隙，进而改变光伏性能，但关于所得结构的细节在很大程度上仍不清楚。在这里，我们研究了Bi取代的CsSnBr中的这些效应。进行了粉末X射线衍射（XRD）和固态Sn、Cs和Bi核磁共振（NMR）光谱分析，以推断Bi取代如何改变这些化合物的结构。Bi取代后立方钙钛矿结构得以保留，但在原子水平上B位出现无序。Bi原子在取代Sn原子时随机分布，没有Bi偏析的迹象。根据电子结构计算，Bi取代后光谱中的吸收边从1.8 eV移至1.2 eV，保持直接带隙。结果表明，Bi取代通过抑制Sn的氧化提高了抗降解能力。
