Ambipolar charge transport

Babel, A., Wind, J.D. and Jenekhe, S.A., Ambipolar charge transport in air-stable polymer blend thin-film transistors, Adv. Func. Mater, 14, 891-898, 2004. 

Exploitation of the push-pull effect of the conjugated pyrrolo[3,4-]pyrrole monomer unit afforded ambipolar charge transport polymers where the dipolar nature of the fused pyrrole units and the planar thiophene comonomers lead to a highly aggregated, pi-stacked conformation, even when the... 

H. Hayashi, W. Nihashi, T. Umeyama, Y. Matano, S. Seki, Y. Shimizu, H. Imahori, Segregated donor-acceptor columns in liquid crystals that exhibit highly efBcient ambipolar charge transport. J. Am. Chem. Soc. 133, 10736-10739 (2011)... 

An ambipolar charge transport was observed in transistors based on HD-PPTV. In contrast, only a hole transport mechanism was observed in HD-PPPV. Field-effect transistors that were fabricated from HD-PPTV showed hole and electron mobilities of 0.2 and 0.03 cm V s Integration of the ambipolar HD-PPTV transistors into complementary inverters showed sharp switching characteristics with voltage gains up to 27. 

Tuladhar, S.M., D. Poplavskyy, S.A. Choulis, J.R. Durrant, D.D.C. Bradley, and J. Nelson. Ambipolar charge transport in films of methanofiillerene and poly(phenylenevinylene)/methanofiiUerene blends. Adv Futic Mater 15 1171. 

The lack of the bipolar transport in binary blends of polymers for most of the compositions shows that controlling the thin-film morphology is challenging. Therefore, the key issue is to realize an interpenetrating and bicontinuous networks of binary polymer blends in order to establish ambipolar charge transport. 

Like 65a-f, cyclic voltammetry data for 67d,e, 73, and 76 showed that these molecules readily accept electrons at low voltages. Thiophene substitution results in a slight shift of reductimi potentials to more negative values with respect to nonthiophene derivative 73, as well as a small decrease in band gap. In addition, the authors obtained device data for these IF dione derivatives in OTFTs. For example, films of 76 showed ambipolar charge transport, having electron and hole mobilities reaching 0.01 and 6 x 10 cvc fW s, respectively. 

Single crystal OFETs were fabricated with microcrystals of 87j as the active channel [77]. With Au source/drain contacts and Au electrodes, the OFET showed ambipolar charge transport, with saturation hole and electron mobilities of 7 X 10 and 3 x 10 cm W S, respectively. 

Concurrent with the Haley studies, Yamashita et al. reported the synthesis and properties of 6,12-diarylindeno[l,2-h]fluorenes 87k-m as well as 87a (Scheme 26) [78]. While their molecules exhibited redox amphoterism as well, the Japanese authors reported only a single oxidation and reduction wave for each. Vapor-deposited thin film OFETs of 87k,1 also showed ambipolar charge transport but at diminished mobilities (hole 1.9 x 10 and 1.1 x 10 crn fV s, respectively electron 8.2 x 10 and 1.6 X 10 cm W-s, respectively). 

Chen Z, Lemke H, Albert-Seifried S, Caironi M, Nielsen MM, Heeney M, Zhang W, McCulloch 1, Sirringhaus H (2010) High mobihty ambipolar charge transport in polyselenophene conjugated polymers. Adv Mater 22 2371-2375... 

A concurrent report from the Yamashita group described the synthesis and characterization of 6,12-diarylindeno[l,2-f)]fluorenes 28k,r-t [72]. OFETs fabricated from thin films of the 28k exhibited hole transport. The 2,6-difluorophenyl 28r and 9-anthracenyl 28t derivatives had deeper LUMO energy levels and, as a result, showed ambipolar charge transport. The field-effect mobility was on the order of 10 cm s most likely due to the amorphous nature of the thin films. Further derivatization and device optimization was anticipated to improve the performance. 

A series of copolymer between dithienylvinylene and phthalimide (P17 in Table 17.3) is reported by Kim et al. (2013). For this series of polymers, the electron withdrawing phthalimide is inserted into the polythiophene backbone. Both polymers display a melt-like thermal transition at 260 °C and 293 °C, respectively and no LC mesophase is observed. The HOMO and LUMO energy levels of the polymers are determined to be —5.2 and —3.3 eV, respectively. Both polymers exhibit ambipolar charge transport behaviour in the OFET transistor device. For P17a, the best hole mobility (pi,) of 0.75 cm is obtained after... 

Kreouzis, T., et til. High mobility ambipolar charge transport in a cross-linked reactive mesogen at room temperature. Appl. Phys. Lett. 87(17), 172110 (2005)... 

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