Transient currents in copper phthalocyanine layers

Ziółkowska, B.; Lipiński, A.

doi:10.1016/0040-6090(82)90256-5

Cited by 40 publications

(6 citation statements)

References 14 publications

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“…A significant charge carrier mobility in the order of 10 À4 cm 2 V À1 Á s À1 can be obtained, which is within the same order compared to the value observed for CuPc crystalline film by Micielski W. et al [15] The investigation of CuPc morphology by using TEM showed aggregates formed by large spherical crystalline domains of $60 nm, which may help to rationalize the high charge carrier mobility in this hyper-branched system. The fast displacement of charge carriers and large carrier mobility also support the high dielectric response observed at high frequency in this dendrimer system.…”

supporting

confidence: 57%

Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

Guo

Yan

2008

Advanced Materials

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Novel copper phthalocyanine (CuPc) materials have potential applications in solar cells, fuel cells, optical-limiting materials, gas sensors and field-effect transistors. [1][2][3][4][5][6][7][8][9][10] Most recently there have been interests in applications for high dielectric constant material for capacitors. [11,12] For example, Zhang et al. have reported a dielectric constant of $48 at 1 MHz in an electrostrictive polymeric CuPc/Polyvinylidenefluoridetrifluoroethylene-chlorofluoroethylene P(VDF-TrFE-CFE) composite.[11] However, a relatively high dielectric loss (>0.4) exists in such system due to the percolation limit of the CuPc filler. More recently, we have observed a very high intrinsic dielectric constant, coupled with a small dielectric loss (<0.01 up to 1MHz) in a newly developed hyper-branched CuPc dendrimer. [12] Although numerous reports have demonstrated the dielectric performance of CuPc polymers, the understanding of the electronic and optical behavior in dendrimers is limited, which is essential in the development of new materials. In this communication, the charge carrier mobility of a newly developed CuPc dendrimer is investigated. The synthesis of the CuPc dendrimer has been previously reported and is shown in Scheme 1. [12] This hyper-branched CuPc has dendritic-like structure consisting of four -CN groups incorporating into the CuPc core. Moreover, our previous experience in the study of triarylamine-based dendrimers and ladder oligomers using the ultra-fast spectroscopy suggested a coherent energy migration process occurred and polaron delocalization states are possible.[13] Time-resolved spectroscopy measurement has been carried out to study the optical behavior of this dendrimer. Our investigation has suggested the formation of delocalized polarons in the system. The super-conjugation effect from the oxygen atom and an increase of system packing through the self-assembling of phthalocyanine rings give polaron hopping and polaron tunneling between phthalocyanine rings. In order to probe the electronic properties of this dendrimer, we carried out time-of-flight measurements to investigate the electron mobility. CuPc dendrimer was first dissolved in N, N-dimethylacetymide (DMAc) solution at a concentration of 1 mg mL À1, then the CuPc/DMAc solution was drop-cast on a silicon wafer with a thickness of 500 mm. After drying in a vacuum oven at 120 8C for several hours, a dendrimer film with a thickness ranging between 4 to 5 mm was obtained using a surface profiler. Further details of the procedure are in the experiment section.A typical transient current at an applied field of 5 V at several different temperatures is depicted in Figure 1 plotted on a linear scale. The transient current signals at room temperature follow a plateau region after a fast decay, then slowly tail off. This shows the characteristics of non-dispersive charge carrier transport. However, upon lowering the temperature, an apparent transition from non-dispersive to dispersive charge carrier transport occurs, which indicat...

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confidence: 57%

Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

Guo

Yan

2008

Advanced Materials

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“…The relationship between capacitance and the reciprocal film thickness is linear, with the slope of εA. The derived value of ε is 4.071×10 -11 Fm -1 , which is in good agreement with available literature values: 3.19×10 -11 Fm -1 [20,21] and 2.12 -4.5 ×10 -11 Fm -1 [22,23] for CuPc. The derived values of ε will be used in the analysis of the remaining reported measurements.…”

Section: Ohmic Conduction and Sclc Measurements 3 31 Capacitance -Vsupporting

confidence: 89%

Electrical Transport Properties of Thermally Evaporated Phthalocyanine (H2Pc) Thin Films

2005

Egyptian Journal of Solids

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Thin films of H 2 Pc of various thicknesses have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity calculations were carried out at different temperatures in the range 298-473 K. Measurements of thermoelectric power confirm that H 2 Pc thin films behave as a p-type semiconductor. The current density-voltage characteristics of H 2 Pc at room temperature showed ohmic conduction mechanism at low voltages. At higher voltages the space-chargelimited conduction (SCLC) accompanied by an exponential trap distribution was dominated. The temperature dependence of current density allows determination of some essential parameters such as the hole mobility (µ h), the total trap concentration (N t), the characteristic temperature (T t) and the trap density P (E).

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“…1 the variation of capacitance C with voltage U for forward bias (top Au positive) and reverse bias (bottom Au positive) are shown and it is clear that the capacitance C does not change with the variation of applied voltage U . This suggests that the total width of the PbPc layer is depleted and the system behaves as a simple capacitor of capacitance C given by [22,23]forCuPc, and 1.77 x lo-'' F m-l [24] for ZnO/Sn composites. The derived value of E will be used later in the following analysis.…”

Section: Capacitance-voltage Measurementsmentioning

confidence: 99%

Ohmic and Space-Charge-Limited Conduction in Lead Phthalocyanine Thin Films

Ahmad

Collins

1991

Phys. Stat. Sol. (a)

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The electrical characteristics of thermally evaporated triclinic lead phthalocyanine thin films are studied. A number of parameters is evaluated on the basis of the theory of space-charge-limited conduction and the following values are obtained: permittivity E = 3.16 x lo-'' F m-'; hole mobility p x 6.05 x lo-'' m2 V-' s-';room temperature hole concentration p o z 1.60 x 10" m -3 ; concentration of traps per unit energy range at the valence band edge Po z 2.79 x J -' m^3; temperature parameter of trapping distribution IT; x 770 K; total trap concentration N, x 2.97 x The room temperature electrical conductivity o = 1.55 x lO-'OS m-'. C -U measurements confirm that the Au-PbPc interface does not form a Schottky barrier. At low temperatures the capacitance of Au-PbPc-Au devices is temperature insensitive, increasing rapidly above 300 K and saturating at about 400 K. Measurements of thermoelectric power confirm that semiconduction is p-type. Die elektrischen Eigenschaften von thermisch aufgedampften dunnen triklinen Blei-Phtalozyaninschichten werden untersucht. Eine Anzahl von Parametern wird auf der Grundlage der Theorie des raumladungsgegrenzten Stromes berechnet und folgende Werte erhalten: Dielektrizitatskonstante E = 3,16 x lo-" F m -I ; Locherbeweglichkeit p z 6,05 x lo-'' m 2 V-'s-'; Raumtemperaturlocherkonzentration p o z 1,60 x 10" m-3; Konzentration der Haftstellen pro Energieeinheit an der Valenzbandkante Po z 2,79 x J-' m -3 ; Temperaturparameter der Haftstellenverteilung ?; = 770 K; Gesarnthaftstellenkonzentration N, z 2,97 x loz3 ~t -~. Die elektrische Leitfahigkeit bei Zimmertemperatur betragt u = 1,55 x 10l o S m -I . C-U-Messungen bestatigen, dal3 die Au-PbPc-Grenzflache keine Schottky-Barnere bildet. Bei tiefen Temperaturen ist die Kapazitat von Au-PbPc-Au-Bauelementen temperaturunabhangig, steigt oberhalb 300 K schnell an und sattigt bei etwa 400 K. Messungen der Thermospannung bestatigen den p-Halbleitungstyp.

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Transient currents in copper phthalocyanine layers

Cited by 40 publications

References 14 publications

Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

Electron Mobility in a Novel Hyper‐branched Phthalocyanine Dendrimer

Electrical Transport Properties of Thermally Evaporated Phthalocyanine (H2Pc) Thin Films

Ohmic and Space-Charge-Limited Conduction in Lead Phthalocyanine Thin Films

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