Theoretical Study on Charge Transport Properties of Intra- and Extra-Ring Substituted Pentacene Derivatives

Abstract

A series of pentacene derivatives, halogen-substituted and thiophene- and pyridine-substituted, have been studied with a focus on the electronic properties and charge transport properties using density functional theory and classical Marcus charge-transfer theory. The transport properties of holes and electrons have been studied to get insight into the effect of halogenation and heteroatom substitution on transport and injection of charge carriers. The calculation results revealed that fluorination and chlorination can effectively lower the lowest unoccupied molecular orbital (LUMO) level, modulate the hole and electron reorganization energy, improve the stacking mode of the crystal structure, and enhance the ambipolar characteristic. Chlorination gives a better ambipolar characteristic. On the basis of halogen substitution, the substitution of terminal benzene ring of triisopropyl-silylethynyl-pentacene (TIPS-PEN) by a thiophene or pyridine will greatly lower the LUMO level and improve the stacking mode, leading to more suitable ambipolar materials. Hence, both intra- and extra-ring substitution are favorable to enhance the ambipolar transport property of TIPS-PEN.

Halogenated Tetraazapentacenes with Electron Mobility as High as 27.8 cm2 V−1 s−1 in Solution‐Processed n‐Channel Organic Thin‐Film Transistors

“…The increased electron reorganization energy of 4F‐TAP is attributable to enhancement of the breathing (at ≈1328 cm −1 ) and stretching vibrations (at ≈1452 and ≈220 cm −1 ) of its pentacyclic framework besides the stretching of CF bonds as shown in Figure S10 (Supporting Information). The effect of Cl substituents on the reorganization energy is negligible in Cl‐TAP and 2Cl‐TAP and small in 4Cl‐TAP, in agreement with the earlier finding that the weaker CCl bond, instead of the CF bond, attached to pentacenes can attenuate the additional contribution to the reorganization energy for electron transfer . The substitution with four chlorine atoms in 4Cl‐TAP is found to suppress the breathing (at ≈1305 cm −1 ) and stretching (at ≈1467 and ≈172 cm −1 ) vibrations of the pentacyclic framework of 4Cl‐TAP as shown in Figure S10 (Supporting Information).…”

γ‐Herringbone Polymorph of 6,13‐Bis(trimethylsilylethynyl)pentacene: A Potential Material for Enhanced Hole Mobility

“…Thus, polymorph 2 shows potential for ambipolar transport with reasonably significant values for both electron and hole mobility. This observation is in accordance with experimental and computational reports on ambipolar transport in peri ‐substituted pentacene. The angular variation of mobility in the b*c* plane can be deciphered from Figure , which depicts the angular resolution anisotropic mobility calculated for 1 and 2 .…”

“…Also, with partly retained edge-to-faceh erringbone-like packing, as in pure pentacene crystals, polymorph 2 is observed to support higher hole mobility (m h = 3.7 cm 2 V À1 s À1 )t han that of 1 (m h = 0.1 cm 2 V À1 s À1 ). Thus, polymorph 2 shows potentialfor ambipolar transport with reasonably significant values for both electron and hole mobility.T his observation is in accordance with experimental [51] and computational [52] reports on ambipolar transport in peri-substituted pentacene. The angular variation of mobility in the b*c* plane can be deciphered from Figure 4, whichd epictst he angular resolution anisotropic mobility calculated for 1 and 2.T he calculated anisotropic hole mobility in both 1 and 2 reaches a maximum value along the direction of p-stacking (q = 08), which itself is assumed to be the axis of reference (crystallographic a*a xis;F igure 1g and h).…”

Theoretical Studies on Novel Gridspiroarenes: Structures, Noncovalent Interactions and Reorganization Energies

“…Hence, it is necessary to study organic semiconductors with excellent charge transfer properties. Theoretical approaches have been an important way for designing a new class of organic optoelectronic materials …”