Frenkel-Holstein Hamiltonian applied to absorption spectra of quaterthiophene-based 2D hybrid organic-inorganic perovskites.
Frenkel-Holstein Hamiltonian applied to absorption spectra of quaterthiophene-based 2D hybrid organic-inorganic perovskites.
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DOI：
10.1063/1.5139044
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
S. Janke;M. Qarai;V. Blum;F. Spano
中科院分区：
文献类型：
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作者：
S. Janke;M. Qarai;V. Blum;F. Spano
对于典型的二维杂化有机-无机钙钛矿（2D HOIPs）（AE 4 T）PbX 4（X = Cl，Br和I），我们证明了Frenkel-Holstein哈密顿量（FHH）可以用来描述有机组分的吸收光谱.我们首先使用四个最近邻耦合的有机人字形晶格中的非等效分子之间的FHH拟合参数的光谱模型。接下来，我们使用线性响应时间依赖密度泛函理论（LR-TDDFT）计算分子跃迁密度，从扩展激子耦合的基础上评估的原子位置内的二维HOIP。我们发现，这两种方法重现实验观察到的光谱，包括它们的形状和峰位的变化。光谱的变化与激子耦合从X = Cl到X = I的减少相关。重要的是，LR-TDDFT为基础的方法与扩展的激子耦合不仅给出了更好的协议与实验的吸收线形状比使用一组有限的拟合参数的方法，但也允许我们将激子耦合的变化与底层的几何形状。因此，我们发现从X = Cl到Br到I的激子耦合的减少是由于分子分离的增加，这反过来又与Pb-X键长从Cl到I的增加有关。我们的研究开辟了一个潜在的途径，从从头计算预测新的2D HOIP的光电性能，并从2D HOIP吸收光谱洞察结构关系。
For the prototypical two-dimensional hybrid organic-inorganic perovskites (2D HOIPs) (AE4T)PbX4 (X = Cl, Br, and I), we demonstrate that the Frenkel-Holstein Hamiltonian (FHH) can be applied to describe the absorption spectrum arising from the organic component. We first model the spectra using only the four nearest neighbor couplings between translationally inequivalent molecules in the organic herringbone lattice as fitting parameters in the FHH. We next use linear-response time-dependent density functional theory (LR-TDDFT) to calculate molecular transition densities, from which extended excitonic couplings are evaluated based on the atomic positions within the 2D HOIPs. We find that both approaches reproduce the experimentally observed spectra, including changes in their shape and peak positions. The spectral changes are correlated with a decrease in excitonic coupling from X = Cl to X = I. Importantly, the LR-TDDFT-based approach with extended excitonic couplings not only gives better agreement with the experimental absorption line shape than the approach using a restricted set of fitted parameters but also allows us to relate the changes in excitonic coupling to the underlying geometry. We accordingly find that the decrease in excitonic coupling from X = Cl to Br to I is due to an increase in molecular separation, which in turn can be related to the increasing Pb-X bond length from Cl to I. Our research opens up a potential pathway to predicting optoelectronic properties of new 2D HOIPs from ab initio calculations and to gain insight into structural relations from 2D HOIP absorption spectra.