论文标题
无机钙钛矿纳米晶体吸收的一光子吸收：一项理论研究
One-photon absorption by inorganic perovskite nanocrystals: A theoretical study
论文作者
论文摘要
The one-photon absorption cross section of nanocrystals (NCs) of the inorganic perovskite CsPbBr$_{3}$ is studied theoretically using a multiband $\mathbf{k}\cdot\mathbf{p}$ envelope-function model combined with a treatment of intercarrier correlation by many-body perturbation theory.首先在Hartree-fock（HF）近似中描述了一个密封的激子，然后通过计算到电子 - 光子相互作用的一阶顶点校正来包括电子和孔之间的相关性。发现顶点校正可增强接近阈值的吸收横截面的增强，相对于横截面的HF（平均场）值4，对于边缘长度$ L = 9 $ -12 nm的NC（中等监督状态）。发现顶点校正增强因子随着激子能量的增加而降低。相对于HF值，能量$ω= 3.1 $ eV的光子的吸收横截面仅1.4-1.5倍。 $ \ mathbf {k} \ cdot \ mathbf {p} $更正对吸收横截面也很重要；发现它们以$Ω= 3.1 $ eV的横截面增加了约30％，相对于有效质量近似中的值。假设凯恩参数$ e_ {p} = 20 $ eV的理论吸收横截面在$ω= 3.1 $ eV处，发现在一组测量值（几乎通过一个数量级）中属于中间，并且可以遵守powerlaw依赖$σ^{（1）（1）} $ incto $ ntendence $ ntimence。 实验。对理论指数2.9的主要贡献被证明是最终状态激子的密度。这些计算中的主要理论不确定性在于凯恩参数$ e_ {p} $的值。
The one-photon absorption cross section of nanocrystals (NCs) of the inorganic perovskite CsPbBr$_{3}$ is studied theoretically using a multiband $\mathbf{k}\cdot\mathbf{p}$ envelope-function model combined with a treatment of intercarrier correlation by many-body perturbation theory. A confined exciton is described first within the Hartree-Fock (HF) approximation, and correlation between the electron and hole is then included in leading order by computing the first-order vertex correction to the electron-photon interaction. The vertex correction is found to give an enhancement of the near-threshold absorption cross section by a factor of up to 4 relative to the HF (mean-field) value of the cross section, for NCs with an edge length $L=9$-12 nm (regime of intermediate confinement). The vertex-correction enhancement factors are found to decrease with increasing exciton energy; the absorption cross section for photons of energy $ω=3.1$ eV (about 0.7 eV above threshold) is enhanced by a factor of only 1.4-1.5 relative to the HF value. The $\mathbf{k}\cdot\mathbf{p}$ corrections to the absorption cross section are also significant; they are found to increase the cross section at an energy $ω=3.1$ eV by about 30% relative to the value found in the effective-mass approximation. The theoretical absorption cross section at $ω=3.1$ eV, assuming a Kane parameter $E_{P}=20$ eV, is found to be intermediate among the set of measured values (which vary among themselves by nearly an order of magnitude) and to obey a power-law dependence $σ^{(1)}(ω)\propto L^{2.9}$ on the NC edge length $L$, in good agreement with experiment. The dominant contribution to the theoretical exponent 2.9 is shown to be the density of final-state excitons. The main theoretical uncertainty in these calculations is in the value of the Kane parameter $E_{P}$.
