Molecular dynamics (MD) simulations have been coupled to valence bond/Hartree-Fock (VB/HF) quantum-chemical calculations to evaluate the impact of diagonal and off-diagonal disorder on charge carrier mobilities in self-assembled one-dimensional stacks of a perylene diimide (PDI) derivative. The relative distance and orientation of the PDI cores probed along the MD trajectories translate into fluctuations in site energies and transfer integrals that are calculated at the VB/HF level. The charge carrier mobilities, as obtained from time-of-flight numerical simulations, span several orders of magnitude depending on the relative time scales for charge versus molecular motion. Comparison to experiment suggests that charge transport in the crystal phase is limited by the presence of static defects.
[Show abstract][Hide abstract] ABSTRACT: We address the calculation of charge carrier mobility of liquid-crystalline columnar semiconductors, a very promising class of materials in the field of organic electronics. We employ a simple coarse-grained theoretical approach and study in particular the temperature dependence of the mobility of the well-known triphenylene family of compounds, combining a molecular-level simulation for reproducing the structural changes and the Miller-Abrahams model for the evaluation of the transfer rates within the hopping regime. The effects of electric field, positional and energetic disorder are also considered. Simulations predict a low energetic disorder (~0.05 eV), slightly decreasing with temperature within the crystal, columnar and isotropic phases, and fluctuations of the square transfer integral of the order of 0.003 eV(2). The shape of the temperature-dependent mobility curve is however dominated by the variation of the transfer integral and barely affected by the disorder. Overall, this model reproduces semi-quantitatively all the features of experimentally measured mobilities, on one hand reinforcing the correctness of the hopping transport picture and of its interplay with system morphology, and on the other suggesting future applications for off-lattice modeling of organic electronics devices.
[Show abstract][Hide abstract] ABSTRACT: Perylene diimide (PDI) and its derivatives hold great promise, since they are undeniably considered as an important family of organic n-type semiconductors with both high carrier mobilities and air stabilities comparable to p-type ones, although they traditionally stand out as a class of high-performance dyes and pigments. In this feature article, we summarize the influences of substituents on different positions (imide, ortho, bay) of PDI on their electronic and morphological (packing) properties, which are in close connection with the ability for carrier transport. Then representative molecular packing motifs for PDIs are also classified, with an emphasis on the intricate interplay of intermolecular interactions, packing motifs and electron transport properties of perylene imide related carrier transport materials from a theoretical point of view, towards paving the way for boosting and improving the electron transport mobilities and air stabilities of PDIs-based materials.
[Show abstract][Hide abstract] ABSTRACT: Columnar stacks of N,N′-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI)n can host meso-tetrakis(4-sulfonatophenyl)porphyrin zinc tetrapotassium salt (ZnTPPSK4) molecules at different ratios through the ionic and π–π interactions prompted by an aqueous environment. Photoexcitation of this host–guest complex generates very fast charge separation (1.4 × 1012 s–1). Charge recombination is markedly decelerated by a probable electron delocalization mechanism along the long-range of tightly stacked TAIPDIs (4.6 × 108 s–1), giving an exceptional kCS/kCR ratio of 3000 as determined by using time-resolved transient absorption techniques.
The Journal of Physical Chemistry C 10/2012; 116(44):23274–23282. DOI:10.1021/jp308549w · 4.77 Impact Factor
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