Browsing by Author "Vishrutha, K.S."

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    Cyanopyridone-cored fluorophores with triphenylamine peripheries: From molecular design to OLED fabrication studies
    (Elsevier B.V., 2023) Vishrutha, K.S.; Ulla, H.; Raveendra Kiran, M.; Badekai Ramachandra, B.R.; Vasudeva Adhikari, A.
    Amongst many types of fluorescent organic materials, compounds with π-conjugation between an electron donor (D) and electron acceptor (A) have been intensively investigated as effective organic electroluminescence (EL) device components. Herein, we report the synthesis and structural characterization of a new series of D-A-D configured small molecule-based fluorophores (TPA-CyP1-7) having triphenylamine (TPA) as a donor unit and 3-cyanopyridine-2-one (CyP) as an acceptor core with different architects for use as efficient yellow light emitters in fluorescent organic light-emitting diodes (OLED). The detailed photophysical, solvatochromic, thermal, electrochemical, and EL properties, including quantum chemical calculations, were systematically investigated to study their relation between structure and properties. All the fluorophores show high fluorescent quantum yields in the solid film state and display high thermal stability with decomposition temperatures above 350 °C. The study reveals that they possess appropriate HOMO and LUMO energies level for effective charge injection. Finally, these yellow luminogens were employed to fabricate new OLED devices as sole emitters and dopants with CBP host materials. Interestingly, the host–guest devices doped with CBP host emitters show a remarkable improvement in the overall device performance. Among them, the TPA-CyP3-based doped device has achieved a maximum current efficiency (ηc), high power efficiency (ηp), and good external quantum efficiency (ηEQE) of 10.72 cd/A, 7.87 lm/W, and 5.32 %, respectively. © 2022 Elsevier B.V.
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    Utilization of newly configured carbazole-cyanopyridone structural hybrids towards achieving high-performance cyan fluorescent organic light-emitting diodes
    (Royal Society of Chemistry, 2024) Vishrutha, K.S.; Ulla, H.; Raveendra Kiran, M.; Badekai Ramachandra, B.R.; Vasudeva Adhikari, A.V.
    Herein, we report the synthesis, characterization, and device fabrication of novel D-A-D (donor-acceptor-donor) type cyanopyridone-based cyan light-emitting organic materials. These small molecules feature a strong electron-donating N-alkylated carbazole unit affixed to a powerful electron-withdrawing cyanopyridone core that is appended with varying secondary donor groups, producing bipolarity in their structures. All the synthesized molecules were well characterized by employing FT-IR, 1H NMR, and 13C NMR spectroscopy, followed by in-depth photophysical, thermal, electrochemical, and electroluminescent studies. Furthermore, we used the density functional theory (DFT) computational approach in the theoretical investigations to gain deeper insights into their electron cloud distributions and structural features. These fluorophores exhibit emission in the 489-510 nm range accompanied by high Stokes shift values, and their TGA data validate the excellent thermal stability (384 °C). As estimated by cyclic voltammetry, the HOMO and LUMO energy levels were found to be 5.35-5.69 eV and 2.92-3.02 eV, respectively, with band gaps of 2.36-2.74 eV. The optical and electrochemical properties of the luminogens have been successfully fine-tuned by varying the auxiliary donors at the carbazole-cyanopyridine hybrids. Electroluminescent studies proved the compatibility of the novel compounds to be an efficient cyan emissive layer with good performance characteristics. Interestingly, amongst the luminophores, Cz-CyP5 bearing a 4-hydroxyphenyl moiety exhibited a maximum current efficiency of 13.16 cd A−1, high power efficiency of 9.85 lm W−1, and good external quantum efficiency of 5.41%. © 2024 RSC.