Thin Films of Highly Planar Semiconductor Polymers Exhibiting Band-like Transport at Room Temperature

Abstract

We report the observation of band-like transport from printed polymer thin films at room temperature. This was achieved from donor-acceptor type thiophene-thiazole copolymer that was carefully designed to enhance the planarity of the backbone and the resulting transfer integral between the macromolecules. Due to the strong molecular interaction, the printed polymer film exhibited extremely low trap density comparable to that of molecular single crystals. Moreover, the energy barrier height for charge transport could be readily reduced with the aid of electric field, which led formation of extended electron states for band-like charge transport at room temperature.

Precise Extraction of Charge Carrier Mobility for Organic Transistors

“…In contrast, the lateral field induced by V D helps to lower the Schottky barrier (see Figure c). The mobility can be increased by V D , which would be exhibited as V D ‐enhancement . This explains in part why mobility extraction in the linear regime is not preferred because the mobility obtained would be relatively low.…”

“…The mobility value is thus improved and the relevant activation energy is reduced. In some cases, this effect is so significant that the hopping barrier seems to vanish and band‐like charge transport is then observed ( Figure ) . While these high mobility, low activation energy, and band‐like transport characteristics may be appealing, they may not represent the intrinsic characteristics of the OSCs and OFETs to be characterized. iii)When the lateral field becomes comparable to the vertical gate field, the off‐state current may be greatly increased .…”

Microstructural control suppresses thermal activation of electron transport at room temperature in polymer transistors

“…12 Band-like transport in organic materials is now well established in the case of small molecules, both for single crystals 14,15,16,17 and more recently for thin films. 18,19 Likely because of the intrinsically higher degree of disorder in polymer semiconductors, very few cases of inverted temperature activated transport have been demonstrated for p-type polymer devices, 20,21,22,23 and only a single one for ntype ones. 24 The observation of such inverted temperature activation has been so far assigned either to a specific chemical structure, 24 to processing conditions, 20 or to the degree of backbone alignment.…”

“…18,19 Likely because of the intrinsically higher degree of disorder in polymer semiconductors, very few cases of inverted temperature activated transport have been demonstrated for p-type polymer devices, 20,21,22,23 and only a single one for ntype ones. 24 The observation of such inverted temperature activation has been so far assigned either to a specific chemical structure, 24 to processing conditions, 20 or to the degree of backbone alignment. 21,22,23 It is indeed of utmost importance to clarify the conditions necessary to observe the transition from thermal activation towards temperature independent and band-like transport in polymer FETs.…”

Drift of charge carriers in crystalline organic semiconductors

“…This approach could also be used to study the electric-field dependence of drift motion, which is an important topic alongside the temperature dependence. [21] In many experiments, relatively high fields have been achieved with observation of nontrivial field-dependence of mobility. [22] Theoretically, in a perfect 1D system with electric field, the energy eigenstates become localized Wannier-Stark states.…”