Browsing by Author "K M, N.K."

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    Capacitance and impedance spectroscopy studies of polymer light emitting diodes based on MEH-PPV:BT blends
    (Elsevier Ltd, 2019) K M, N.K.; Sterin, N.S.; Das, P.P.; Umesh, G.; Satyanarayan, M.N.
    Light emitting polymer poly [2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) is blended with a wide bandgap electron transport material benzothiadiazole (BT) and its effect on the electronic properties has been studied by capacitance and impedance spectroscopy (IS) in PLEDs. The impedance data is fitted using equivalent circuit models and the minimum parallel resistance (Rp) at zero bias have been obtained for 1:3 ratio of MEH-PPV:BT blended devices. The negative capacitance (NC) shows the occurrence of the trap-assisted non-radiative recombination mechanism at low frequencies in the unblended MEH-PPV PLEDs. Further, this behavior is seen to be reduced in PLEDs with MEH-PPV:BT blends. This clearly suggests that the blending of MEH-PPV and BT at different weight ratios results in the suppression of trap-assisted recombination. This can be attributed to the elimination of trap states due to the dilution of semiconductor material on account of the addition of wide bandgap host material. Moreover, the blended devices have shown a significant improvement in the conductivity at small bias voltages. © 2019 Elsevier B.V.
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    New blue light emitting cyanopyridine based conjugated polymers: From molecular engineering to PLED applications
    (Elsevier B.V., 2019) Pilicode, N.; K M, N.K.; Acharya, M.; Naik, P.; N, S.M.; Vasudeva Adhikari, A.V.
    In this work, we report the design of three new cyanopyridine scaffold based polymers, viz. TPy 1-3 as potential blue light emitters for PLED applications. The new polymer design comprise, a cyanopyridine core as an electron accepting entity, thiophene as an electron donating unit with different auxiliary donors, viz. phenylene (TPy 1 ), biphenyl (TPy 2 ), and fluorene (TPy 3 ), and have been synthesized, following standard synthetic protocols including Suzuki-cross coupling polymerization reaction. Further, in order to assess all the prerequisites to act as an active emitter, the polymers TPy 1-3, were subjected to structural, thermal, linear optical, electrochemical and computational studies. The results revealed that, all the polymers were thermally stable up to 300 ?C and their estimated optical band-gaps were found to be 2.59–2.80 eV. Finally, new polymer light emitting diode (PLED) were fabricated by employing the polymers TPy 1-3, as active emissive material with a configuration of ITO/PEDOT: PSS/Polymer/Al. Interestingly, all the fabricated devices, exhibited an intense blue electroluminescence at 12 V with low threshold voltages of 4.2–4.8 V, signifying an effective injection of electron in the device. © 2019 Elsevier B.V.