Monte Carlo study of charge transport in organic sandwich-type single-carrier devices: Effects of Coulomb interactions

Scaling theory for percolative charge transport in molecular semiconductors: Correlated versus uncorrelated energetic disorder

“…This was shown by Zhou et al for uncorrelated disorder 23 and by van der Holst et al for correlated disorder. 24 We note that these works show that at higher concentration, around 10%, these interactions cannot be neglected.…”

Simulating charge transport in organic semiconductors and devices: a review

“…This is important when considering high charge density (i.e. approaching 1 charge per 100 sites) [128] and charge transport across a heterojunction [121] where short-range Coulomb interactions [129] have been shown to be important. Casalegno et al [127] describe a method which allows partial consideration of Coulomb interactions in ME, although this poses additional numerical challenges to implement self-consistently.…”

“…Extraction of charges from the semiconductor is a hopping process with the charge in energy set equal to the difference in energy between the site (including electrostatic interactions) and the Fermi level of the electrode. Injection, by contrast, is included by considering an array of charges stationed outside the device which can hop into the adjacent semiconductor [48,129,144]. In some cases the injection hops are restricted to the first layer of OSC sites within the device [48], consistent with nearest-neighbour hopping, or successive OSC layers into the device with an exponentially decreasing rate [144], consistent with variable-range hopping.…”

“…If charge transport is being modelled in the context of a device, one must ensure that the voltage boundary conditions at the electrodes are maintained by including additional 'image charges,' which are the reflection of charges in the OSC in the plane of the electrodes. Indeed, image charges of image charges (and so on) are required to strictly enforce voltage boundary conditions [129,142], although these are sometimes ignored with no apparent impact on predictive capability [143]. The computational burden of calculating Coulomb interactions is significant, hence a number of authors have developed techniques to balance accuracy with run time as discussed further in section 2.3.3.…”

“…Using this approach Casalegno et al [142] were able to speed up OPV simulations by a factor of more than 7. An alternative approach is to in calculate Coulomb interactions explicitly for particle separations smaller than rc, and as layer-averaged quantities for particle separations > rc [129,202]. Although one has to be careful to ensure that charges are not double-counted [129], this approach allows one to trade-off speed and the accuracy of long-range Coulomb interactions through choice of rc.…”