Biega Raisa-Ioana, Filip Marina R, Leppert Linn, Neaton Jeffrey B
Institute of Physics, University of Bayreuth, Bayreuth 95440, Germany.
Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom.
J Phys Chem Lett. 2021 Mar 4;12(8):2057-2063. doi: 10.1021/acs.jpclett.0c03579. Epub 2021 Feb 19.
Halide double perovskites with alternating silver and pnictogen cations are an emerging family of photoabsorber materials with robust stability and band gaps in the visible range. However, the nature of optical excitations in these systems is not yet well understood, limiting their utility. Here, we use many-body perturbation theory within the approximation and the Bethe-Salpeter equation approach to calculate the electronic structure and optical excitations of the double perovskite series CsAgBX, with B = Bi, Sb and X = Br, Cl. We find that these materials exhibit strongly localized resonant excitons with energies from 170 to 434 meV below the direct band gap. In contrast to lead-based perovskites, the CsAgBX excitons are computed to be non-hydrogenic with anisotropic effective masses and sensitive to local field effects, a consequence of their chemical heterogeneity. Our calculations demonstrate the limitations of the Wannier-Mott and Elliott models for this class of double perovskites and contribute to a detailed atomistic understanding of their light-matter interactions.
具有交替银和氮族元素阳离子的卤化物双钙钛矿是一类新兴的光吸收材料，具有强大的稳定性和可见光范围内的带隙。然而，这些体系中的光学激发本质尚未得到很好的理解，限制了它们的实用性。在这里，我们使用近似下的多体微扰理论和贝叶斯 - 萨尔皮特方程方法来计算双钙钛矿系列CsAgBX（其中B = Bi、Sb，X = Br、Cl）的电子结构和光学激发。我们发现这些材料表现出强烈局域化的共振激子，其能量比直接带隙低170至434毫电子伏特。与铅基钙钛矿不同，计算得出CsAgBX激子是非类氢的，具有各向异性的有效质量且对局部场效应敏感，这是其化学不均匀性的结果。我们的计算证明了万尼尔 - 莫特和埃利奥特模型对这类双钙钛矿的局限性，并有助于对其光与物质相互作用进行详细的原子层面理解。
