Predictions of Hole Mobilities in Oligoacene Organic Semiconductors from Quantum Mechanical Calculations

Abstract

We estimate the hole mobility for oligoacene crystals using quantum mechanics (QM) to calculate the reorganization energy and electron-transfer coupling matrix elements and molecular dynamics (MD) to do the thermal averaging. Using an incoherent transport model we calculate a hole mobility of 6.5 cm 2 /(V s) for pentacene crystals at 300 K. This can be compared to recent experimental results of 5 cm 2 /(V s). However, we find that an alternative packing into the crystal could lead to a hole mobility of 15.2 cm 2 /(V s). This suggests that current materials might still be improved by a factor of ∼3. Such calculations might be useful for finding solid-state structures that would increase the hole mobility for use in high-performance molecular devices.

Push-pull effect on the geometrical, optical and charge transfer properties of disubstituted derivatives of mer-tris(4-hydroxy-1,5-naphthyridinato) aluminum (mer-AlND3)

“…In these calculations only the structural modification of the molecules are considered neglecting the polarization effect in the surrounding medium. The electron/hole transport is predictable from the electron (λ ele )/hole (λ hole ) reorganization energies and in general has good agreement with the experimental observations [27,71,82,[85][86][87][88][89][90][91][92][93][94][95]. Previously the reorganization energies for hole/ electron of mer-Alq3 and its derivatives [56,57,59,61,63] and mer-AlND3 [64] has been calculated at B3LYP/6-31G(D) level.…”

“…Using this model the charge transport that is calculated here is the intermolecular process in which the charge hops between two molecules. The hole and electron transport process at the molecular level in the electroluminescent layer can then be portrayed as the electron transfer/hole transfer reactions between the neighboring molecules as [27,[84][85][86][87][88][89][90][91][92][93][94][95]:…”

BODIPY derivatives as n-type organic semiconductors: Isomer effect on carrier mobility

“…At room temperature, it is generally accepted that the transport in organic materials occures via charge carrier hopping between adjacent molecules. Assuming no correlation between charge hopping events and charge motion is a homogeneous random walk, the maximum values of drift mobility for charge carrier (hole/electron) transport in semiconductor can be written as [28,49]. …”

“…For the ideal high-purity crystals without disorder, the orientations of the molecules surrounding each molecule are identical, so that Eq. (9) leads to the orientation function describing the mobility in a specific conducting direction on a specific surface in organic single crystal [28,49].…”

“…p-Type organic semiconductors such as pentacene, rubrene and derivatives of them have been investigated widely [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The recently improved theoretical understandings of organic semiconductors have even addressed the design rule of organics with high hole mobilities [28][29][30][31]. However, n-type semiconductors are not fully developed, and their field effect transistors (FETs) performance is not satisfactory yet.…”