Current–voltage sweep for the 100 nm pentacence film after positive (△) and negative (▾) bias stress, measured at 75 °C. After positive bias stress, current flow under positive applied voltages increases, while after negative voltage stress, current flow under negative applied voltage increases. The diode-like behavior is reversed in direction, but comparable in magnitude.
Conductance of the 100 nm pentacene film as a function of applied voltage after positive (a) and negative (b) bias stress. Measurements were taken at five temperatures between 30 °C and 75 °C. Although the conductance is relatively constant at high voltages, the system is clearly not Ohmic as the conductance is observed to change rapidly yet smoothly between −10 V and 10 V.
The activation energy, calculated from the temperature dependence of the conductance data as G = G 0 exp(−E a/kT), is shown as a function of applied voltage for the pentacene film after positive (◯) and negative (●) bias stress. The activation energy varies over a range of 0.5 eV to 1.0 eV depending on the magnitude and polarity of the applied voltage as well as the direction of the bias stress.
The Arrhenius prefactor, G 0, plotted against the activation energy, E a, after positive (◯) and negative (●) bias stress. The Meyer-Neldel rule is observed for both datasets. The Meyer-Neldel temperature, calculated from the linear regression of ln(G 0) vs E a, is 123 °C. The extrapolated conductance at the Meyer-Neldel temperature is 8.9 × 10−12 S.
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