The (Non-)Local Density of States of Electronic Excitations in Organic Semiconductors by Carl R. Poelking

Author:Carl R. Poelking
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Even though electrostatic effects in organic semiconductors have been linked to the molecular quadrupole in a variety of theoretical and experimental studies [18, 23–28, 30–32], the routine use of an interaction range cutoff resulted in a very different and significantly more local interpretation of electrostatic effects, as will be illustrated in the following section.

Fig. 4.3Hole and electron energy profiles with and without long-range correction. Position-dependent electrostatic and induction contribution to hole (h) and electron (e) site energies for a C/D5M crystal-crystal interface (a) in the semiconverged regime (cluster size 12 nm) and b in the 2D-converged regime with infinite interaction range. The insets illustrate the system configuration used in the respective computation (spherical cluster or thin film). The level diagrams (c, d) for the two regimes differ qualitatively with respect to level bending and offset. The level alignment obtained for the 12 nm clusters (c) leads to trapping of holes at the interface and extraction of electrons towards the donor rather than acceptor. The long-range corrected scenario (d) provides flat energy profiles and offsets suited for a functional photovoltaic device (for illustration of gradients, blue circles represent electrons, red circles holes). Note that the cutoff procedure employed in a and c includes an electrostatic buffer shell which guards against parasitic polarization effects at the cluster edges

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