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Impedance Characterization of Organic Light‐Emitting Structures with Thermally Activated Delayed Fluorescence
Author(s) -
Voitsekhovskii Alexander V.,
Nesmelov Sergey N.,
Dzyadukh Stanislav M.,
Kopylova Tatya.,
Degtyarenko Konstantin M.
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900847
Subject(s) - materials science , oled , capacitance , electrical impedance , anode , equivalent circuit , cathode , voltage , optoelectronics , biasing , fluorescence , analytical chemistry (journal) , layer (electronics) , optics , chemistry , electrode , electrical engineering , composite material , physics , chromatography , engineering
The organic light‐emitting device (OLED) structures based on layer (2,8‐bis[ N , N ‐di(4 methoxyphenyl)amino]dibenzothiophene‐ S , S ‐dioxide) with thermally activated delayed fluorescence (TADF) are created. The properties of TADF‐based structures are studied by measuring the impedance under various conditions (100 Hz–2 MHz and 10–300 K). The features of the capacitance–voltage curves of the studied structures can be explained by the simultaneous injection of holes from the anode and electrons from the cathode. Cole–Cole plots are studied at various voltages and temperatures. It is shown that at forward bias voltages, the impedance is determined by single relaxation process and at low voltages by more than one process. An OLED equivalent circuit consisting of four serial capacitance–resistance (CR) chains (CR–CR–CR–CR) is proposed. Using this circuit allows us to achieve good agreement between the calculated and experimental frequency dependences of the impedance at various voltages. The different elements of the equivalent circuit are associated with different layers in a multilayer OLED structure. The dependences of the CR element values on the bias voltage are found, and the thicknesses of the corresponding layers are determined.