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| Format: | Preprint |
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2023
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| Online-Zugang: | https://arxiv.org/abs/2311.16289 |
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| _version_ | 1866929211992702976 |
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| author | Candiotto, Graziâni Giro, Ronaldo Horta, Bruno A. C. Rosselli, Flávia P. de Cicco, Marcelo Achete, Carlos A. Cremona, Marco Capaz, Rodrigo B. |
| author_facet | Candiotto, Graziâni Giro, Ronaldo Horta, Bruno A. C. Rosselli, Flávia P. de Cicco, Marcelo Achete, Carlos A. Cremona, Marco Capaz, Rodrigo B. |
| contents | Organic light-emitting diodes (OLEDs) devices in the archetype small molecule fluorescent guest-host system tris(8-hydroxyquinolinato) aluminum (Alq$_{3}$) doped with 4-(dicyanomethylene)-2-methyl-6-julolidyl-9-enyl-4H-pyran (DCM2) displays a redshift in light-emission frequency which is extremely sensitive to the dopant concentration. This effect can be used to tune the emission frequency in this particular class of OLEDs. In this work, a model is proposed to describe this effect using a combination of density functional theory (DFT) quantum-chemical calculations and stochastic simulations of exciton diffusion via a Förster mechanism. The results show that the permanent dipole moments of the Alq$_{3}$ molecules generate random electric fields that are large enough to cause a non-linear Stark shift in the band gap of neighboring DCM2 molecules. As a consequence of these non-linear shifts, a non-Gaussian probability distribution of highest-occupied molecular orbital to lowest-unoccupied molecular orbital (HOMO-LUMO) gaps for the DCM2 molecules in the Alq$_{3}$ matrix is observed, with long exponential tails to the low-energy side. Surprisingly, this probability distribution of DCM2 HOMO-LUMO gaps is virtually independent of DCM2 concentration into Alq$_{3}$ matrix, at least up to a fraction of 10%. This study shows that this distribution of gaps, combined with out-of-equilibrium exciton diffusion among DCM2 molecules, are sufficient to explain the experimentally observed emission redshift. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2311_16289 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Emission Redshift in DCM2-Doped Alq$_{3}$ Caused by Non-Linear Stark Shifts and Förster-Mediated Exciton Diffusion Candiotto, Graziâni Giro, Ronaldo Horta, Bruno A. C. Rosselli, Flávia P. de Cicco, Marcelo Achete, Carlos A. Cremona, Marco Capaz, Rodrigo B. Materials Science Mesoscale and Nanoscale Physics Organic light-emitting diodes (OLEDs) devices in the archetype small molecule fluorescent guest-host system tris(8-hydroxyquinolinato) aluminum (Alq$_{3}$) doped with 4-(dicyanomethylene)-2-methyl-6-julolidyl-9-enyl-4H-pyran (DCM2) displays a redshift in light-emission frequency which is extremely sensitive to the dopant concentration. This effect can be used to tune the emission frequency in this particular class of OLEDs. In this work, a model is proposed to describe this effect using a combination of density functional theory (DFT) quantum-chemical calculations and stochastic simulations of exciton diffusion via a Förster mechanism. The results show that the permanent dipole moments of the Alq$_{3}$ molecules generate random electric fields that are large enough to cause a non-linear Stark shift in the band gap of neighboring DCM2 molecules. As a consequence of these non-linear shifts, a non-Gaussian probability distribution of highest-occupied molecular orbital to lowest-unoccupied molecular orbital (HOMO-LUMO) gaps for the DCM2 molecules in the Alq$_{3}$ matrix is observed, with long exponential tails to the low-energy side. Surprisingly, this probability distribution of DCM2 HOMO-LUMO gaps is virtually independent of DCM2 concentration into Alq$_{3}$ matrix, at least up to a fraction of 10%. This study shows that this distribution of gaps, combined with out-of-equilibrium exciton diffusion among DCM2 molecules, are sufficient to explain the experimentally observed emission redshift. |
| title | Emission Redshift in DCM2-Doped Alq$_{3}$ Caused by Non-Linear Stark Shifts and Förster-Mediated Exciton Diffusion |
| topic | Materials Science Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2311.16289 |