期刊
ADVANCED OPTICAL MATERIALS
卷 9, 期 14, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adom.202002153
关键词
OLED; organic light‐ emitting diode; solid‐ state solvation effect; SSSE; TADF; thermally activated delayed fluorescence
资金
- German Research Foundation (DFG) [MA 3342/6 1]
- European Research Council (ERC) under the European Union's Horizon 2020 Research and Innovation Program [679 213]
- Projekt DEAL
Organic light-emitting materials with thermally activated delayed fluorescence (TADF) show promise in enhancing display applications. Recent studies have focused on intermolecular effects between emitting molecules, particularly the impact of solid-state solvation or aggregation on sample performance. By controlling emitter concentration, device performance can be tuned, with potential for improved efficiency in organic light-emitting diodes (OLEDs).
Organic light-emitting materials exhibiting thermally activated delayed fluorescence (TADF) show great promise for improving display applications. Recently, intermolecular effects between emitting molecules have been given more attention, revealing strong solid-state solvation or aggregation induced changes of sample performance. Implications of this on device performance are not yet fully covered. In this work, a thorough investigation of a novel TADF emitter, methyl 2,3,4,5,6-penta(carbazol-9-yl)benzoate (5CzCO2Me), is provided. Steady-state emission spectra reveal a luminescence redshift with increasing emitter concentration in a small molecule host. In all investigated concentrations, the emission profile remains the same; thus, the redshift is attributed to the solid-state solvation effect. The highest photoluminescence quantum yield (PLQY) is achieved in the 20 wt% sample, reaching 66%. The best organic light-emitting diode (OLED) in terms of current-voltage-luminance and external quantum efficiency (EQE) parameters is the device with 60 wt% emitter concentration, reaching maximal EQE values of 7.5%. It is shown that the emitter transports holes and that charge-carrier recombination does not take place on the bandgap of the host, but rather, a mixed host-guest concentration-dependent recombination is seen. The hole-transporting properties of 5CzCO2Me allow for a new dimension in tuning the device performance by controlling the emitter concentration.
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