Direct Observation of the Exciton Self-Trapping Process in CsCu2I3 Thin Films
| Autor: | Jörn Schmedt auf der Günne, Thomas Lenzer, Mirko Scholz, Ke Xu, Marius Morgenroth, Kawon Oum, Robin Kentsch |
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| Rok vydání: | 2020 |
| Předmět: |
Photoluminescence
Materials science Band gap Exciton 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Molecular physics 0104 chemical sciences Condensed Matter::Materials Science Ultrafast laser spectroscopy General Materials Science Direct and indirect band gaps Charge carrier Physical and Theoretical Chemistry Thin film 0210 nano-technology Absorption (electromagnetic radiation) |
| Zdroj: | The Journal of Physical Chemistry Letters. 11:4286-4291 |
| ISSN: | 1948-7185 |
| Popis: | Low-dimensional copper halides, such as CsCu2I3, have emerged as promising LED materials featuring strongly Stokes-shifted photoluminescence with high quantum yield. Previous calculations suggest an exciton self-trapping mechanism; however, direct experimental evidence for this process is still lacking. Here, we present femtosecond UV-vis transient absorption experiments of CsCu2I3 thin films. The films were analyzed by SEM, XRD, and 133Cs/63Cu NMR for crystallinity and defects. Unique spectral dynamics is observed. The band gap absorption exhibits a characteristic double-peak structure arising from the 130 meV spin-orbit splitting of the copper d electrons. Emission at the direct band gap disappears because of the formation of the lowest-energy self-trapped exciton state. We determined the time constant of 12 ps for the trapping process of thermally relaxed free excitons, with an energy barrier of at least 60 meV. The data are successfully modeled by global kinetic analysis, providing also accurate time constants for charge carrier cooling processes. |
| Databáze: | OpenAIRE |
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