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Mechanochromic and thermally activated delayed fluorescence dyes obtained from D–A–D′ type, consisted of xanthen and carbazole derivatives as an emitter layer in organic light emitting diodes

Nasiri, S ; Sharif University of Technology | 2022

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  1. Type of Document: Article
  2. DOI: 10.1016/j.cej.2021.131877
  3. Publisher: Elsevier B.V , 2022
  4. Abstract:
  5. In this study, we designed, engineered and investigated two new thermally activated delayed fluorescence (TADF) dyes obtained from D–A–D′ type, consisted of 2-(9H-carbazol-9-yl)-3-(3-methoxy-9H-carbazol-9-yl)-9H-xanthen and 2-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3-(3-methoxy -9H-carbazol-9-yl)-9H-xanthen. In these dyes, xanthen derivative and carbazole derivatives have played important roles as an acceptor and two unsymmetrical donor units. In addition, the photophysical properties of these dyes were evaluated by the UV–VIS absorption, photoluminescence spectroscopy and photoluminescence decay lifetime analysis in solution, initial dye, non-doped and doped solid state (neat–film) at different temperatures and under the vacuum-ambient. Substitution's strong effect of the donor units was impressive; where, the dyes' ionization potential values were achieved as 5.53 and 5.62 eV. The charge mobility measurements of dyes were carried out using two different methods of space charge–limited current (SCLC) and time of the flight (TOF). Appropriate extracted results proved dyes' promising application as an emitter layer in organic light emitting diodes (OLEDs), through the photophysical properties, aggregation induced emission enhancement (AIEE) phenomenon, and high intensity of emission spectrum spanning the large part of visible area and good thermal stability. The solution process and physical evaporation deposition (PVD) procedure were tandemly performed in order to coat the layers and fabricate non-doped and doped OLEDs. The low turned on voltage' values of OLEDs were recorded in the range of 4.08 to 5.31 V. Furthermore, the maximum values of brightness, current, power and external quantum efficiency were achieved as 72565 cd/m2, 37.32 cd/A, 20.99 lm/W and 13.41%, respectively. © 2021 Elsevier B.V
  6. Keywords:
  7. Mechanochromic ; Organic light emitting diodes ; TEM ; Thermally activated delayed fluorescence ; Xanthen derivative ; Electroluminescence ; Emission spectroscopy ; Fluorescence ; Ionization potential ; Luminance ; Photoluminescence ; Photoluminescence spectroscopy ; Polycyclic aromatic hydrocarbons ; Carbazol ; Carbazole Derivatives ; D types ; Emitter layers ; Fluorescence dyes ; Methoxy ; Thermally activated delayed fluorescences ; Organic light emitting diodes (OLED)
  8. Source: Chemical Engineering Journal ; Volume 430 , 2022 ; 13858947 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S1385894721034549