Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
4 results
Search Results
Item Electrical Characterization of Hybrid Hetero Interface using n-ZnO and p-CuPc(Elsevier Ltd, 2015) Raveendra Kiran, M.R.; Ulla, H.; Fernandes, J.M.; Satyanarayan, M.N.; Umesh, G.In the present work we report the fabrication, current density-voltage (J-V) characteristics, capacitance-voltage characteristics and impedance measurements of the n-ZnO nanoparticles/ p-CuPc hybrid junction. ZnO nanoparticles were synthesized by sol-gel method. The J-V characteristics clearly show the diode like behaviour. The junction behaviour has been investigated using surface topography (AFM), capacitance and electrical impedance studies. © 2015 Elsevier Ltd.Item Investigation of hole-injection in ?-NPD using capacitance and impedance spectroscopy techniques with F4TCNQ as hole-injection layer: Initial studies(Academic Press, 2014) Fernandes, J.M.; Raveendra Kiran, M.R.; Ulla, H.; Satyanarayan, M.N.; Umesh, G.The charge accumulation leading to injection at the organic interface in the sequentially doped hole-only device structure is studied using capacitance and impedance based spectroscopic techniques. In this paper, we investigate the role of p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the charge transport properties of N,N'-Di(1-naphthyl)-N,N'-diphenyl-(1,1?-biphenyl)-4,4?-diamine (?-NPD) through sequential deposition. We show that the hole injection into ?-NPD increases with the increase of interlayer (F4TCNQ) thickness by correlating the current density-voltage, capacitance-voltage, capacitance-frequency and impedance measurements. © 2014 Elsevier Ltd. All rights reserved.Item Investigation of hole transport in ?-NPD using impedance spectroscopy with F4TCNQ as hole-injection layer(Academic Press, 2015) Fernandes, J.M.; Raveendra Kiran, M.R.; Ulla, H.; Satyanarayan, M.N.; Umesh, G.The charge carrier transport is studied in N,N?-di(1-naphthyl)-N,N?-diphenyl-(1,1?-biphenyl)-4,4?-diamine (?-NPD) with the incorporation of sequentially doped p-type dopant 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) as hole-injection layer in hole-only device structures. The field dependent mobility of the charge carriers is determined using frequency dependent capacitance, conductance and impedance methods by varying the thickness of ?-NPD. The Poole-Frenkel zero-field mobility and the Poole-Frenkel coefficient thus obtained for each device in all the three methods is found to be almost constant. © 2015 Elsevier Ltd. All rights reserved.Item Optoelectronic properties of novel alkyl-substituted Triphenylamine derivatives(Elsevier B.V., 2017) Fernandes, J.M.; Swetha, C.; Appalnaidu, E.; Navamani, K.; Rao, V.J.; Satyanarayan, M.N.; Umesh, G.Hole transport characteristics in three new organic compounds based on triphenylamine (TPA) moiety are presented. The effect on electrical and optical properties of TPA, attached with methyl or tert-butyl side groups, has been investigated through measurement of current density versus voltage (J-V), capacitance versus voltage (C-V), frequency dependent capacitance, ac conductivity, Impedance spectroscopy, UV-Vis spectroscopy, Photoluminescence (PL) spectroscopy and X-Ray Diffraction (XRD) studies. These measurements reveal that, the attachment of methyl or tert-butyl group in the para-position of the TPA moiety leads to improved optoelectronic properties and greater molecular stability. XRD analysis of the samples indicates that the inter-molecular distance is the lowest for TPA with tert-butyl side group (3.43 Å) as compared to pure TPA (3.57 Å). This leads to stronger inter-molecular interaction as evidenced by the UV-Vis spectra. PL studies indicate significant Quantum Efficiency (?30%) for alkyl attached TPA. In order to get a better understanding of the charge transport phenomena, the effect of molecular structure dynamics on charge transfer kinetics is analyzed by evaluating the charge carrier hopping rate coefficient and dynamic state factor. The dynamic state factor b has higher value for lower bias voltage, corresponding to dc conductivity, whereas, at higher bias, the value of b is smaller, indicating the dominance of ac conductivity. Hopping conductivity is seen to be highest for the device with tert-butyl substitution in TPA moiety. Our experiments indicate an order of magnitude enhancement in charge carrier mobility for alkyl-substituted TPA. © 2017 Elsevier B.V.