(Color online) Representative I−V characteristics of pentacene-based organic diodes. The inset illustrates the diode structure with Au/pentacene/Al on a glass substrate.
(Color online) Impedance-voltage (Z−V) data showing fully depleted organic layer in the reverse-bias regime. The active area of both diodes is 4.3 × 10−4 cm2. (a) Z−V characteristics of the diode with 515 nm of pentacene. (b) Z−V characteristics of the diode with 1012 nm of pentacene.
MIM type energy diagram of a pentacene diode at different operation regimes. (a) Reverse-bias regime, (b) thermal equilibrium, (c) flat-band condition, (d) bulk-limited forward-bias regime. The lower panel indicates the dominant conduction mechanisms under each bias regime.
(Color online) Simulated potential profiles in the 515-nm pentacene layer. The ionization potential of pentacene is 5.2 eV and the work function of the cathode (Al) is 4.2 eV in all three cases with different hole injection barrier values at the anode; (a) 0.1 eV barrier (work function of Au anode as 5.1 eV), (2) 0.2 eV barrier (work function of Au anode as 5.0 eV), (c) 0.3 eV barrier (work function of Au anode as 4.9 eV).
(Color online) (a) Impedance-frequency (Z-f) data in the complex plane at different forward-bias voltages. The inset shows the equivalent circuit which corresponds to the shape of these curves. (b) Z-f plot with the fitting result using the parallel RC equivalent circuit.
(Color online) (a) Bulk resistance as a function of applied forward-bias. The circles show the resistances calculated from the first derivative of the I−V curve (Fig. 1) and the triangles represent the extracted parameters from the fitting of the Z-f measurements. (b) Fitted capacitance from the Z-f measurements.
(Color online) Extraction method of the dielectric constant of pentacene. Diodes with four different device areas are tested in each set. The measured geometrical capacitance and thickness are multiplied and plotted as a function of the device area. The slope of linear fits to the experimental results gives the average quasistatic dielectric constant multiplied by the permittivity of vacuum.
(Color online) Tapping mode AFM images of pentacene layer on Au electrode (scan size: 2 × 2 μm2); (a) 515 nm of pentacene, (b) 1012 nm of pentacene.
(Color online) Optical microscopic images (a) before I−V measurement and (b) after electrical breakdown due to high applied electric field.
(Color online) Scatter plot showing the variance of the measured Eb of pentacene in 10 diodes around the average value of 1.02 MV/cm.
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