Figure smaller than 1, the disorder induced by Coulomb

Figure 2(a) present the
increasing of the current density by the built-in the applied voltage and at
higher voltages the J-V curve is determined by trap-space-charge limited
mobility and the resistance of the contacts. Since different slope can be found
at different points yielding different transition phase of organic
semiconductors. When comparing the J-V
characteristics for the various temperatures 114K, 145K, 155K, 218K, 247K, 275K
and 296K, transition points are identified with the built-in temperature where
it is up to 217K and the applied voltage is 0.7V. In
order to confirm our results, we report in figure 2(b) the current density
voltage characteristic for the same device at 296K and for two cases of
disorder energy 30meV and 60meV which are presented the transition phase of the
C60 which is transformed from cube centre face to simple cube. Clearly, the
agreement between the results extract from literature and simulations is fairly
well when the disorder energy is 30meV, however for the case of 60meV, there is
a huge gap. Indeed, Coulomb interactions
reduce the charge trapping, but also induce an additional energetic disorder.
When

 is smaller
than 1, the disorder induced by Coulomb interaction is not completely screened
out by the intrinsic disorder of the material. However, when  

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 is larger than 2, the disorder induced by Coulomb
interaction is completely screened out by the intrinsic disorder of the
material; the number of intrinsic low-energy states is large, and the barrier
reduction effect due to Coulomb interactions can be important, leading to an
increase in the charge carrier mobility with density.

Indeed, charge
injection strongly depends on the energy level matching between the Fermi level
of the metal electrodes and organic semiconductors energy levels, low
unoccupied molecular orbital (LUMO) and highest occupied molecular orbital
(HOMO). In this context, we have studied the effect of contact metal on the
current density and the charge carrier mobility of the active layer (SubPc/C60) which is sandwiched
between the two metal electrodes. We have used PEDOT:PSS and BCP hole and
electron electrodes, respectively. These materials are employed to inject one type of charge carriers into
the semiconductor layer seen figure 3.