Tailoring Hot Exciton Dynamics in 2D Hybrid Perovskites through Cation Modification
| Autor: | Sebastian Hurtado Parra, Natasha Iotov, Cherie R. Kagan, James M. Kikkawa, Michael R. Gau, Qinghua Zhao, Patrick J. Carroll, Daniel B. Straus |
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| Rok vydání: | 2020 |
| Předmět: |
Materials science
Photoluminescence Phonon Band gap Exciton FOS: Physical sciences General Physics and Astronomy Applied Physics (physics.app-ph) 02 engineering and technology 010402 general chemistry 01 natural sciences Molecular physics Spectral line Condensed Matter::Materials Science chemistry.chemical_compound Physics - Chemical Physics Atom Phenyl group General Materials Science Chemical Physics (physics.chem-ph) Condensed Matter - Materials Science General Engineering Materials Science (cond-mat.mtrl-sci) Physics - Applied Physics 021001 nanoscience & nanotechnology 0104 chemical sciences Molecular geometry chemistry 0210 nano-technology |
| Zdroj: | ACS Nano. 14:3621-3629 |
| ISSN: | 1936-086X 1936-0851 |
| DOI: | 10.1021/acsnano.0c00037 |
| Popis: | We report a family of two-dimensional hybrid perovskites (2DHPs) based on phenethylammonium lead iodide ((PEA)$_2$PbI$_4$) that show complex structure in their low-temperature excitonic absorption and photoluminescence (PL) spectra as well as hot exciton PL. We replace the 2-position (ortho) H on the phenyl group of the PEA cation with F, Cl, or Br to systematically increase the cation's cross-sectional area and mass and study changes in the excitonic structure. These single atom substitutions substantially change the observable number of and spacing between discrete resonances in the excitonic absorption and PL spectra and drastically increase the amount of hot exciton PL that violates Kasha's rule by over an order of magnitude. To fit the progressively larger cations, the inorganic framework distorts and is strained, reducing the Pb-I-Pb bond angles and increasing the 2DHP band gap. Correlation between the 2DHP structure and steady-state and time-resolved spectra suggests the complex structure of resonances arises from one or two manifolds of states, depending on the 2DHP Pb-I-Pb bond angle (as)symmetry, and the resonances within a manifold are regularly spaced with an energy separation that decreases as the mass of the cation increases. The uniform separation between resonances and the dynamics that show excitons can only relax to the next-lowest state are consistent with a vibronic progression caused by a vibrational mode on the cation. These results demonstrate that simple changes to the structure of the cation can be used to tailor the properties and dynamics of the confined excitons without directly modifying the inorganic framework. Comment: 39 pages |
| Databáze: | OpenAIRE |
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