Faculty Publications
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Item Optical and electrochemical properties of a new donor-acceptor type conjugated polymer derived from thiophene, carbazole and 1,3,4-oxadiazole units(Trans Tech Publications Ltd ttp@transtec.ch, 2010) Manjunatha, M.G.; Vasudeva Adhikari, A.V.; Hegde, P.K.A new donor-acceptor type poly[3-{5-[3,4-didecyloxy-5-(1,3,4-oxadiazol-2- yl)thiophen-2-yl]-1,3,4-oxadiazol-2-yl}-9-dodecyl-9H-carbazole] (P) has been synthesized starting from thiodiglycolic acid and 9H-carbazole through multistep reactions. The polymer has been synthesized through precursor polyhydrazide route. The weight average molecular weight of the polymer was found to be 7210. The polymer exhibited intense green fluorescence in solid sate. Cyclic voltammetric experiments showed that the polymer has low-lying LUMO (-3.55 eV) and high lying HOMO (-5.77 eV) energy levels due to the presence of alternate donor and acceptor units. The optical and electrochemical studies reveal that the new polymer (P) is a promising material for the development of polymer light emitting diodes (PLEDs). © (2010) Trans Tech Publications.Item New cyanopyridine based conjugated polymers carrying auxiliary electron donors: From molecular design to blue emissive PLEDs(Elsevier Ltd, 2020) Pilicode, N.; Naik, P.; K M, K.M.; Acharya, M.; Satyanarayan, M.N.; Vasudeva Adhikari, A.V.Three new D-A (Donor-Acceptor) configured conjugated polymers, i.e. PPy1-3, centered on strong electron accepting cyanopyridine scaffold carrying varied auxiliary donors, viz. phenylene (PPy1), biphenyl (PPy2), and fluorene (PPy3) were designed and synthesized as blue emitters for PLEDs. The new polymers were subjected to spectral, thermal, photophysical and electrochemical characterization. Also, computational studies (DFT) were performed on the repeating units of polymer using Turbomole 7.2 V software package at the B3LYP/TZVP hybrid levels. Further, their weight average molecular masses were found to be 38.8 kDa, 38.9 kDa and 57.7 kDa, respectively as determined by GPC technique. Furthermore, the new polymers PPy1-3, were shown to be stable thermally up to 308–374 °C. Evidently, they exhibited good photophysical behavior with their optical energy band gaps of 2.53–2.64 eV. Finally, the polymers PPy1-3 were employed as an active emissive layer in standard ITO/PEDOT:PSS/Polymer/Al configured PLEDs. Interestingly, at 12 V all the newly fabricated devices exhibit a stable blue characteristic electroluminescence with low threshold voltages of 3.40–5.20 V, confirming an efficient injection of electrons in the diodes. From the results, it is clear that, the polymers PPy1-3, can be considered as prospective blue light emitters for PLED application. © 2019 Elsevier LtdItem Synthesis, characterization and electroluminescence studies of cyanopyridine-based ?-conjugative polymers carrying benzo[: C] [1,2,5]thiadiazole and naphtho[1,2- c:5,6- c ?]bis([1,2,5]thiadiazole) units(Royal Society of Chemistry orders@rsc.org, 2020) Pilicode, N.; Naik, P.; Acharya, M.; Vasudeva Adhikari, A.V.Four new donor-acceptor type cyanopyridine-based conjugative polymers, i.e.TDPy1-4, carrying different electron-donating aromatic/heteroaromatic moieties in the backbone were synthesized from their respective co-monomers by using the Suzuki cross-coupling polycondensation protocol. These polymers were designed to possess good control of color emission and to have balanced charge injection, and transport properties. Their structures were confirmed by spectroscopic studies and their thermal stability was evaluated using the TGA technique. The photophysical, electrochemical and electroluminescence properties of these materials were established in order to assess their suitability for PLED applications. DFT-based computational studies were performed to verify and elucidate the above-said properties. Evidently, they demonstrate good green fluorescence with optical band gap (Eg) values of 2.14-2.27 eV. Finally, new PLEDs based on TDPy1-4 were fabricated with a structure of ITO/PEDOT:PSS/polymer/Al, wherein they are able to act as green light emitters with stable electroluminescence behaviors. © 2020 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Nicotinonitrile centered luminescent polymeric materials: Structural, optical, electrochemical, and theoretical investigations(John Wiley and Sons Inc, 2020) Pilicode, N.; Naik, P.; Vasudeva Adhikari, A.V.Herein, we describe the design, synthesis, and structural characterization of three new push-pull type conjugative polymers, that is, VPPy1-3 comprising strong electron-withdrawing N-heterocyclic nicotinonitrile scaffold coupled with electron-donating phenylene units through vinylene bridges, as promising candidates for optoelectronic applications. They were successfully synthesized from their respective co-monomers by simple polycondensation synthetic routes, viz. Knoevenagel and Wittig reactions. All the polymers were subjected to photophysical, electrochemical, thermal, and theoretical studies in order to ascertain their suitability in polymer light-emitting diode applications as blue emitters. Evidently, they are readily soluble in most of the organic solvents, enabling them easy solution-processable. These new polymers display strong blue photoluminescence at the peak in the range of 431 to 462 nm with a wide optical bandgap in the order of 2.55 to 2.63 eV. The obtained electrochemical data were employed to evaluate their HOMO/LUMOs. The density functional theory calculations generated useful information on their FMO, molecular geometries, and electronic properties. Also, the influence of their structural modification on the above-said properties was discussed in detail to reveal the structure-property relationship. Conclusively, these results illustrate the great prospective of this class of polymeric materials for the application in solution-processable blue LEDs. © 2020 Society of Plastics EngineersItem New cyanopyridine-based ?-conjugative poly(azomethine)s: Synthesis, characterization and electroluminescence studies(John Wiley and Sons Ltd, 2021) Pilicode, N.; Naik, P.; K M, K.M.; Acharya, M.; Satyanarayan, M.N.; Vasudeva Adhikari, A.V.Four new Schiff-base type conjugative polymers (CPs), that is, Py1-4 carrying a strong electron-withdrawing cyanopyridine scaffold coupled with different electron-donating aromatic/heteroaromatic moieties were synthesized from their respective co-monomers by simple poly-condensation route. They were subjected to structural, thermal, photophysical, and electrochemical characterizations and theoretical investigations in order to identify their suitability in polymer light-emitting diode (PLED) application. All these polymers showed good film-forming ability and exhibited favorable photophysical behaviors with an optical bandgap in the order of 2.54-2.68 eV. Further, their electrochemical data were used to evaluate highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels. Finally, Py1-4 were successfully employed as blue-light emitter in the construction of new ITO/PEDOT:PSS/ Py1-4/Al configured light-emitting diodes (LED), and the fabricated devices demonstrated stable blue electroluminescence behavior endorsing an effective electrons injection in the PLEDs. © 2020 John Wiley & Sons LtdItem New green emitters based on push-pull type pyrene substituted cyanopyridones: Design strategies and utilization in organic light-emitting diodes(Elsevier Ltd, 2023) K S, V.; Ulla, H.; M, R.K.; Badekai Ramachandra, B.R.; Vasudeva Adhikari, A.V.A novel series of D-A-D type conjugated dyes (Py-CyP1-7) centred on a strongly electron-withdrawing cyanopyridone scaffold (A) linked to highly electron-donating pyrene unit (D) and varied auxiliary donors (D) were designed and synthesized, for applications in green organic light-emitting diodes (OLEDs). All the hybrids were systematically subjected to theoretical, optical, electrochemical, and thermal studies to validate their efficiency in behaving as green emitters. Finally, we employed the dyes as sole and dopant emitters in OLEDs. The OLED with 3 wt % Py-CyP4 in the CBP host shows maximum efficiencies of 14.38 cd A−1, 12.04 lm W−1, and 5.91%. © 2023Item 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.