Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 097...
Upcoming SlideShare
Loading in …5
×

Temperature dependent electrical response of orange dye complex based

226 views

Published on

  • Be the first to comment

  • Be the first to like this

Temperature dependent electrical response of orange dye complex based

  1. 1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME269TEMPERATURE DEPENDENT ELECTRICAL RESPONSE OFORANGE-DYE COMPLEX BASED SCHOTTKY DIODESyed Abdul Moiz 1, Ahmed M. Nahhas21(Department of Electrical Engineering, Faculty of Engineering and Islamic Architecture,Umm Al Qura University, Makkah, Saudi Arabia)2(Department of Electrical Engineering, Faculty of Engineering and Islamic Architecture,Umm Al Qura University, Makkah, Saudi Arabia)ABSTRACTIn order to investigate the temperature dependent electrical response of Orange-Dyecomplex, Schottky diodes were fabricated from solution with spin coating method. From theircurrent-voltage response it is observed that Schottky diode follows space charge limitedcurrent model. Therefore, by applying space charge limited current model different chargetransport parameters such as trap factor, mobility, and threshold voltage and trap density aredetermined and their response as a function of temperature are investigated and discussed. Itis observed that all charge transport parameters improves at elevated temperature withingiven temperature range. This study will help us to understand the nature of Orange DyeComplexes for their future applications.Keywords: Orange Dye, Organic Semiconductor, Charge Injection, Schottky diode & SCLCmodel.I. INTRODUCTIONOrganic semiconducting based electronic devices have already received considerableattention by different groups of researchers and technologists due to many advantages such aslight weight, flexible, require simple fabrication technology, low cost, deposited on varioussubstrate and many other advantages [1-4]. Despite their pronounced improvement andcurrently at the early stage of commercialisation, some of the fundamental features of chargetransport process are still not clear and required comprehensive understanding [5-8].INTERNATIONAL JOURNAL OF ELECTRONICS ANDCOMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)ISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 4, Issue 2, March – April, 2013, pp. 269-279© IAEME: www.iaeme.com/ijecet.aspJournal Impact Factor (2013): 5.8896 (Calculated by GISI)www.jifactor.comIJECET© I A E M E
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME270Charge transport process inside the organic semiconductor plays a vital role to define theefficiency of electronic devices. Under the influence of applied potential, electrons andholes are injected from metal to organic semiconductor layer and are hoped from onelocation to the other location inside the organic semiconductor as charge transportprocess. Both charge injection and hopping transport process are very complex in natureand depends on many other factors, but some of such factors can be characterized as afunction of temperature [9, 10].Broadly speaking, the electrical response of organic semiconductor can be classifiedeither as injection limited or bulk limited depends on the limitation imposed by either thebarrier at metal-organic semiconductor interface or by the bulk semiconductor itself forhopping process. Generally, the mobility of organic semiconductor is very low ascompared to other inorganic semiconductor; therefore most of the cases the chargetransport limitation is imposed by the bulk nature of semiconductor itself to defined theirelectrical response [11]. In bulk limited charge transport process, injected chargesoccupies organic space between electrodes for longer period of time and make spacecharge region, such phenomena can be modelled by space charge limited current (SCLC)to define their electrical response [12].Orange-Dye (C17H17N5O2) with Vinyl-Ehtynyl-Trimehyl-Piperiodole(VETP,C12H19NO) as complex is emerged as novel organic semiconductor and offers manyunique properties which are highly suitable for sensors especially for humidity sensor andphoto-sensors [13-16]. Despite their importance very limited amount of information aboutthis complex is available in literature. Therefore in this study we investigated theelectrical response of OD-VETP complex as a function of temperature and differentcharge transport parameters were evaluated and their behaviour as a function oftemperature is discussed.II. EXPERIMENTALAll chemical were purchases from local market and were used as it is without anyfurther purification. The molecular structure of both OD and VETP are shown in Figure1. OD has molecular weight 323 gm/mole with density 0.9 gm/cm3, while VETP hasmolecular weight 0.6 gm/mole and density 0.6 gm/cm3[14-16]. Both organic materialsare solution in water and make charge transfer complex at room temperature. In order tomake the complex 5% by weight of VETP is mixed in aqueous OD solution and wasstirred in an ultrasound container for more than 1 hour and kept them in an inert nitrogenenvironment for more than 24 hours to settle downs. Meanwhile SnO2 coated glasssubstrate were cleaned and OD-VETP complex were deposited by spin coating method at1000 rpm for 30 second. From simple optical examination it was clearly observed thatgrown thin film showed homogenous surface and their thickness was estimatedapproximately 600 nm. For external electrical characterization, silver metal was depositedover OD-VETP surface in spherical shape with diameter ~6 mm as electrode and thendevices were annealed at 100 oC in inert environment for more than an hour. The cross-sectional diagram of the Schottky diode is shown in Figure 2.
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME271Figure 1. Molecular structure of (a) Orange nitrogen Dye (OD) and (b) VETP complexCurrent-voltage responses of Schottky diode were measured with help of dcmeasurement station with temperature adjusting facilities, where four-probe method wereused for electrical characterization, but for simplicity only two probes are shown in Figure 2.For each 5 oC increments, the electrical properties of diode were measured, wheretemperature measurement were carried out in the range of 25 oC to 80 oC with andexperimental temperature error of ±0.5 oC. By using hot-probe method, it was observed thatOD-VETP complex is a p-type semiconductor just like OD semiconductor.OD-VETPComplexGlass SubstrateSilver ElectrodeSnO2 ElectrodeFigure 2. A schematic cross-sectional view of SnO2 / OD-VETP/ Ag diode
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME272III. RESULTS & DISCUSSIONThe current-voltage characteristics of SnO2/OD-VETP/Ag in forward bias is shown inFigure 3 as a function of temperature from 25, 40, 60 and 80 oC respectively. From thefigure, it is clearly observed that the Schottky diode follows nonlinear typical diodebehaviour in the forward bias. The current passing through the device is sharply rises as afunction of temperature and at 80 oC the maximum value of current 5.5 µA is observed at 10volts, which is nearly 20 times higher than the current passing through the Schottky diode at25oC as same voltage. Generally, VETP is highly resistive semiconductor and therefore OD-VETP complex shows high resistance as compared to OD itself, but still complex material isvery material for many sensor applications [13-16].If we define V as applied voltage then current-density (J) can be defined by SCLCmodel as [17,18],8932dVJ poθµεε= (1)01234560 2.5 5 7.5 10Current(μA)Voltage (Volts)80oC60oC40oC25oCFigure 3. Current-voltage characteristics for SnO2/OD-VETP/Ag Schottky diode at 25, 40,60 and 80 oC respectivelyWhere εr is the relative dielectric constant for OD-VETP complex and can be approximate as3, just like as other organic semiconductor. Similarly εo is standard dielectric constant andequal to the 8.65x10-14F/cm, θ is refer as trap factor, µp is the mobility of hole and d is thethickness of OD-VETP thin film. It is unanimously accepted that the mobility of free carriersinside organic semiconductor, which is direct function of applied electric field, can bedescribed by Poole-Frenkel equation as [19]
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME273( ),exp Eop βµµ = (2)where µo and β can be defined as zero field mobility and Poole-Frenkel factor respectively.Both above discuss models give us valuable information about charge transport mechanismfor organic semiconductor. If we incorporate mobility from equation 2 into the equation, thenequation 1 can be written after some manipulation as( ) ,exp8932dVEJ oo βθµεε= (3)By simple manipulation the equation (3) can be written as [20],89ln 2EdEJo βθµεε +=(4)Where E is applied electric field (V/d). In order to justify the SCLC model, the plotsof ln (J/E2) vs. square root of E are drawn in Figure 4, as a function of temperature. It isobserved that independent of given temperature range the Schottky diode follows SCLCmodel to define their current-voltage response. As OD-VETP complex is a p-type material,therefore we can assume that SnO2 provide ohmic contact to OD-VETP complex, in otherway holes are injected from SnO2 into OD-VETP and forms space charge region insidecomplex. From the both Figure 3 and 4 it is also clear that conductivity inside complexsharply rises with increment of temperature.-26-22-18-14-1050 175 300 425ln(J/E2)(A/E2)[Electric Field (V/cm)]1/280oC60oC40oC25oCFigure 4. In (J/E2) vs. E1/2response for SnO2/OD-VETP/Ag Schottky diode as a function oftemperature 25, 40, 60, and 80 oC respectively
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME274The SCLC can be classified into three regions, depending on voltage. These regionsare termed as (1) ohmic region, (2) trapped charge region, and (3) space charge region. It canobserved from SCLC response of OD-VETP complex that initially the current increases veryslowly and then rises sharply with increment of applied electric field at all temperature [21].The initial region of SCLC is generally considered as high resistive ohmic region and can bemodel as [6,20,21];LVNeJ oohm µ=(5)Where e is the charge (1.6x 10-19C) of hole carriers, No is the free hole density. Withthe increment of voltage, a transition is observed from ohmic region to the trapped spacecharge region and this transition is generally defined at some threshold voltage (VT), alsocalled trapped filled voltage. Figure 5 shows the response of threshold voltage as a functionof temperature for Schottky diode.Figure 5. Threshold voltage behaviour of SnO2/OD-VETP/Ag Schottky diode as a functionof temperatureIt is observed that threshold voltage is linearly decreases as a function of temperaturewith given temperature range, which indicates that the transition of ohmic region to trappedspace charge region for OD-VETP diode is also linearly decreasing with respect totemperature. Threshold voltage for SCLC model can be further defines as [17]
  7. 7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME275.22stTFLdeNVε= (6)Where Nt is defined as trap density (cm-3). Density of these traps is determined forOD-VETP Schottky diode with the help of above equation as a function of temperature. Thetrap density for SnO2/OD-VETP/Ag Schottky diode as a function of temperature is shown inFigure 6. Traps are nothing, just localized states inside organic semiconductor havingcapability to hold carrier for some period of time. These traps are generated due a largenumber of reasons but can be classified as chemical or structural traps. Grains boundary,bond defects, chains ends etc. are termed as structural defects, while traces of chemicalreactants, and incorporation of impurities materials and other environment elements aretermed as chemical traps [22]. These traps can never be eliminated for organic semiconductorbut can be minimized by careful processing during thin film growth and device fabricationprocess. However, these traps are direct function of energy (or temperature), every trap stateis associated with some energy, it can capture only those carriers who have lower energy thentrap associated energy. Therefore when temperature increases the average kinetic energy ofholes are also increases and available trap density is exponentially decreased for theseenergetic carriers as shown in Figure 6.23456720 40 60 80TrapDensity(1020m-3)Temperature (oC)Figure 6. Trap density for SnO2/OD-VETP/Ag Schottky diode as a function of temperatureMobility of holes is another important parameter, which play a very vital role todefine the electric response of OD-VETP complex and can easily be determine from SCLCequation. The actual mobility deviates from ideally mobility by trap factor, and such trapfactor (θ) can be defined as [17]
  8. 8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME276,00+=tpppθ (7)where po (cm-3) and pt (cm-3) are free and trapped carrier density. These carrierdensity and hence trap factor is determine for OD-VETP Schottky diode and are shown inFigure 7. Trap factor is also increases as a function of temperature, and will help us toestimate the actual mobility of OD-VETP complex, which is shown in Figure 8. Like trapfactor, mobility is also exponential function of temperature and are sharply rises at highertemperature. The behaviour of mobility as a function of temperature inside the complex is thecollective response of all above space charge parameters as discussed above. At lowtemperature injected holes face high trap density and only small holes are hopped andsucceeded to reach another electrode, however at higher temperature a large no of trappedcarriers become part of free carriers and hopped to reach opposite electrode to give risehigher mobility and hence current. Similarly, when applied voltage is further increasing,holes receives an extra increasing force to overcome these traps barriers and hence a large noof holes are capable to reach at opposite electrode to give rise higher value of current.Therefore, at higher voltage and temperature higher current is observed for OD-VETPSchottky diode.0.250.3750.50.62520 40 60 80TrapFactor(θ)Temperature (oC)Figure 7. Trap factor as a function of temperature for OD-VETP Schottky diode
  9. 9. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME2770408012016020020 40 60 80Mobility(108cm2/Vsec)Temperature (0C)Figure 8. Mobility of holes as a function of temperature for OD-VETP Schottky diodeIV. CONCLUSIONSIn this study, we have investigated the electrical response of novel OD-VETPcomplex based Schottky diode as a function of temperature from the range of 25 oC to 80 oC.From their current-voltage properties, it was observed that Schottky diode follows spacecharge limited current. Therefore, by applying space charge limited current model, differentcharge transport parameters such as threshold voltage, trap density, trap factor and holemobility were estimated as a function of temperature. It was observed that trap densityexponentially decreases, while threshold voltage also decreases linearly as a function oftemperature. On the other hand, both trap factor and hole mobility are exponentiallyimproved at elevated temperature. At high temperature more and more holes are injected andhopped with higher mobility and faced lower trap density to reach opposite electrode andgive rise higher value for current. This study will help to understand the nature of the OD-VETP and will facilitate to efficiently utilize them for different types of organicsemiconductor based electronic devices.ACKNOWLEDGEMENTSAuthors are thankful to Professor Khasan S Karimov for their comments and valuablesuggestion to improve this study.
  10. 10. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME278REFERENCES[1]. J. Meyer, S. Hamwi, M. Kröger, W. Kowalsky, T. Riedl, A. Kahn, Transition metaloxides for organic electronics: Energetics, device physics and applications, AdvancedMaterials, 24 (40), 2012, 5408-5427.[2]. C. Dimitrakopoulos, P. Malenfant, Organic thin film transistors for large areaelectronics, Advanced Materials, 14 (2), 2002, 99-117.[3]. K. Karimov, M. Ahmed, S. Moiz, M. Fedorov, Temperature-dependent properties oforganic-on-inorganic Ag/p-CuPc/n-GaAs/Ag photoelectric cell, Solar EnergyMaterials and Solar Cells, 87 (1-4), 2005, 61-75.[4]. G. Malliaras, R. Friend, An organic electronics primer, Physics Today, 58 (5), 2005,53-58.[5]. H. Sirringhaus, T. Sakanoue, J. Chang, Charge-transport physics of high-mobilitymolecular semiconductors, Physica Status Solidi (B) Basic Research, 249 (9), 2012,1655-1676.[6]. S. Moiz, M. Ahmed, K. Karimov, M. Mehmood, Temperature-dependent current-voltage characteristics of poly-N-epoxypropylcarbazole complex, Thin Solid Films,516 (1), 2007, 72-77.[7]. S. Moiz, A. Nahhas, H. Um, S. Jee, H. Cho, S. Kim, J. Lee, A stamped PEDOT:PSS-silicon nanowire hybrid solar cell, Nanotechnology, 23 (14), 2012, 145401.[8]. T. Kelley, P. Baude, C. Gerlach, D. Ender, D. Muyres, M. Haase, D. Vogel, S.Theiss, Recent progress in organic electronics: Materials, devices, and processes,Chemistry of Materials, 16 (23), 2004, 4413-4422.[9]. I. Campbell, D. Smith, Electrical Transport in Organic Semiconductor, Int’l J. ofHigh Speed Electronics and Systems, 11 (2), 2001, 223-249.[10]. A. Chempbell, D. Bradley, D. Lidzey, Space Charge Limited Conduction withTraps in Poly (phenylene vinylene) Light Emitting Diode, J. of Applied Physics, 82(12), 1997, 6326-6342.[11]. Y. Peng, J. Yang, Field distribution and criterion for bulk-limited and injection-limited current conduction in single layer organic light-emitting devices, AppliedPhysics A: Materials Science and Processing, 80 (7), 2005, 1511-1516.[12]. D. Nuzzo, S. Van Reenen, R Janssen, M. Kemerink, S. Meskers, Evidence forspace-charge-limited conduction in organic photovoltaic cells at open-circuitconditions, Physical Review B - Condensed Matter and Materials Physics, 87 (8),2013, 085207.[13]. M. Chani, K. Karimov, F. Khalid, S. Abbas, M. Bhatty, Orange dye - polyanilinecomposite based impedance humidity sensors, Chinese Phys. B, 22, 2013, 010701.[14]. M. Ahmed, K. Karimov, S. Moiz, Photoelectric behaviour of n-GaAs/orange dye,vinyl-ethynyl-trimethyl-piperidole/conductive glass sensor, Thin Solid Films, 516(21), 2008, 7822-7827.[15]. K. Karimov, M. Sayyad, M. Ali, M. Khan, S. Moiz, K. Khan, H. Farah, Z. Karieva,Electrochemical properties of Zn/orange dye aqueous solution/carbon cell, Journal ofPower Sources, 155(2), 2006, 475-477.[16]. M. Saleem, K. Karimov, Z. Karieva, A. Mateen, Humidity sensing properties ofCNT-OD-VETP nanocomposite films, Physica E: Low-Dimensional Systems andNanostructures, 43 (1), 2010, 28-32.[17]. P. Mark, W. Helfrich, Space Charge Limited Currents in Organic Crystals, J. ofApplied Physics, 33 (1), 1962, 205.
  11. 11. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME279[18]. S. Moiz, M. Ahmed, K. Karimov, M. Mehmood, Temperature-dependent current-voltage characteristics of poly-N-epoxypropylcarbazole complex, Thin Solid Films,516 (1), 2007, 72-77.[19]. D. Braun, Electronic injection and conduction processes for polymer devices,Journal of Polymer Science, Part B: Polymer Physics, 41 (21), 2003, 2622-2629.[20]. H. Klauk, Organic Electronics: Materials, Manufacturing and Applications, Wiley-VCH Verlag GmbH, Weinheim, 2003.[21]. S. Moiz, M. Ahmed, K. Karimov, F. Rehman, J. Lee, Space charge limited current-voltage characteristics of organic semiconductor diode fabricated at various gravityconditions, Synthetic Metals, 159 (13), 2009, 1336-1339.[22]. T. Nguyen, Defect analysis in organic semiconductors, Materials Science inSemiconductor Processing, 9 (1-3), 2006, 198-203.[23]. K C Sajjan, Muhammad Faisal, Khened B.S and Syed Khasim, “Humidity SensingProperties of Polyaniline/Potassium Molybdate Composites” International Journalof Electrical Engineering & Technology (IJEET), Volume 4, Issue 2, 2013,pp. 179 - 186, ISSN Print : 0976-6545, ISSN Online: 0976-6553.[24]. Ahmed Thabet, “Experimental Investigation on Thermal Electric andDielectric Characterization for Polypropylene Nanocomposites using Cost-FewerNanoparticles”, International Journal of Electrical Engineering & Technology(IJEET), Volume 4, Issue 2, 2013, pp. 1 - 12, ISSN Print : 0976-6545, ISSN Online:0976-6553.

×