High Electron Mobility and Ambipolar Charge Transport in Binary Blends of Donor and Acceptor Conjugated Polymers

Abstract

High electron mobility and ambipolar charge transport are observed in phase‐separated binary blends of n‐type poly(benzobisimidazobenzophenanthroline) (BBL) with p‐type polymer semiconductors, poly[(thiophene‐2,5‐diyl)‐alt‐(2,3‐diheptylquinoxaline‐5,8‐diyl)] (PTHQx) and poly(10‐hexylphenoxazine‐3,7‐diyl‐alt‐3‐hexyl‐2,5‐thiophene) (POT). Atomic force microscopy (AFM) and transmission electron microscopy (TEM) show phase‐separated domains of 50–300 nm in the binary blend thin films. The TEM images and electron diffraction of BBL/PTHQx blends show the growth of single‐crystalline phases of PTHQx within the BBL matrix. A relatively high electron mobility (1.0 × 10–3 cm2 V–1 s–1) that is constant over a wide blend‐composition range is observed in the PTHQx blend field‐effect transistors (FETs). Ambipolar charge transport is observed in both blend systems at a very high concentration of the p‐type semiconductor (≥90 wt % PTHQx or ≥80 wt % POT). Ambipolar charge transport is exemplified by an electron mobility of 1.4 × 10–5 cm2 V–1 s–1 and a hole mobility of 1.0 × 10–4 cm2 V–1 s–1 observed in the 98 wt % PTHQx blend FETs. These results show that ambipolar charge transport and the associated carrier mobilities in blends of conjugated polymer semiconductors have a complex dependence on the blend composition and the phase‐separated morphology.

Molecular Self‐Assembled Monolayers and Multilayers for Organic and Unconventional Inorganic Thin‐Film Transistor Applications

“…[1][2][3] While much of the attention of the organic TFT community has been focused on the search for high-mobility, [4][5][6] ambient stable, [7][8][9] and solution-processable small molecule [10][11][12][13][14][15][16][17] and polymeric [18][19][20] semiconductor materials, [21][22][23][24][25][26][27][28][29][30] it is now clear that substantial improvements in TFT performance can also be achieved by replacing and/or modifying the gate dielectric. [1,[31][32][33][34][35][36] As will be discussed here, self-assembled monolayers (SAMs) and multilayers (SAMTs), such as self-assembled nanodielectrics (SANDs), [37] are gaining significant attention as gate dielectrics due to their robust insulating properties, tunable thicknesses, and efficient solution processability.…”

High‐mobility Ambipolar Transistors and High‐gain Inverters from a Donor–Acceptor Copolymer Semiconductor

“…[1] Ambipolar transistors are also of interest in fundamental studies of charge transport in organic semiconductors [1,6,16] as well as the development of efficient light-emitting transistors. [8,[17][18][19][20][21] Ambipolar transistors have been reported from the active channels of multilayers, [2,22,23] blends or bulk heterojunctions of unipolar organic semiconductors, [3,[11][12][13]17] single active materials with asymmetric metal electrodes of different workfunctions, [20] and single-component materials with a common electrode. [3][4][5][6][7][8][9][10]19,[24][25][26][27][28] Charge-carrier mobilities in the range of 10 À5 to 0.1 cm 2 V À1 s À1 have been reported in the case of ambipolar OFETs based on solution-processable, singlecomponent semiconductors.…”

“…[11] The PNIBT OFETs showed good current modulation with on/off ratios of 10 3 -10 5 at a large source-drain bias (V ds ¼ AE80 V), compared with that typically reported ( 10 3 ) for ambipolar OFETs with comparable mobilities (>10 À3 cm 2 V À1 s À1 ). [5,7,8,12,17,[19][20][21] The charge-carrier mobilities were calculated using the standard saturation region equation of metal-oxide-semiconductor field-effect transistors: [14] …”

Organic Thin‐film Transistors Based on Polythiophene Nanowires Embedded in Insulating Polymer

“…[6][7][8][9][10][11] The use of conjugated polymer blends as active materials has brought a new way to tune and optimize the electronic properties of devices; for example, ambipolar field-effect charge transport has been reported in binary blends of p-and n-type conjugated polymers or oligomers. [12,13] Semiconducting and insulating polymer blends have also attracted increasing interest, because they can combine the electronic properties of semiconducting polymers with the low cost and excellent mechanical characteristics of insulating polymers. However, the presence of the insulating component tends to degrade the device performance by diluting the current density of the film.…”