High-performance non-volatile memory that can operate under various mechanical deformations such as bending and folding is in great demand for the future smart wearable and foldable electronics. Here we demonstrate non-volatile solution-processed ferroelectric organic field-effect transistor memories operating in p-and n-type dual mode, with excellent mechanical flexibility. Our devices contain a ferroelectric poly(vinylidene fluoride-cotrifluoroethylene) thin insulator layer and use a quinoidal oligothiophene derivative (QQT(CN)4) as organic semiconductor. Our dual-mode field-effect devices are highly reliable with data retention and endurance of 46,000 s and 100 cycles, respectively, even after 1,000 bending cycles at both extreme bending radii as low as 500 mm and with sharp folding involving inelastic deformation of the device. Nano-indentation and nano scratch studies are performed to characterize the mechanical properties of organic layers and understand the crucial role played by QQT(CN)4 on the mechanical flexibility of our devices.

A family of copper and zinc phthalocyanine-based amphiphililes possessing racemic and optically active diol units, (rac)-ZnPc(OH)16, (rac)-CuPc(OH)16, and (S)-CuPc(OH)16, have been synthesized. The selfassembling properties of these amphiphiles in aqueous solution have been studied by UV-vis, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopies, X-ray diffraction (XRD) patterns, and transmission electron microscopy (TEM). Only the copper complexes produced fibrous assemblies from aqueous solutions through two noncovalent bondings: π-π interaction among phthalocyanine rings and hydrogen bonds among diol units. The formation of fibrous assemblies strongly depends on the central metal of the phthalocyanine complex. The optically active (S)-CuPc(OH)16 is stacked and arranged in a left-handed helix. The chirality of diol units in (S)-CuPc(OH)16 also affects the intercolumnar lattice of phthalocyanine stacks.

Fabrication of p-n structures is a key issue in a number of electronic devices, including rectifying diodes, solar cells, and bipolar transistors. Complementary metal oxide semiconductor (CMOS) technology based on the integration of discrete p-and n-channel field-effect transistors (FETs) on a same substrate has been widely used in a variety of electronic applications and enables the fabrication of integrated circuits with low-power dissipation and high operational stability. In the growing field of organic electronics, efficient large-scale organic CMOS integrated circuits [1,2] as well as lateral p-n diodes [3] have already been realized by thermally evaporating p-and n-type semiconducting organic molecules separately through shadow masks. Alternatively, fabrication of organic inverters by inkjet printing, self-assembly, or spin-coating has also been reported and has demonstrated the enormous potential of solution processing for low-cost, large-area, flexible electronics. [4][5][6][7][8][9][10] However, in spite of remarkable recent advances in high-mobility organic FET materials [11][12][13][14] and nanostructuration techniques, [15] there has still been no reliable approach for effectively patterning p-n bipolar and CMOS microstructures made from solutionprocessible organic semiconductors. We have addressed this issue by exploiting the unique charge-transport properties of the solution-processible dicyanomethylene-substituted quinoidal quaterthiophene [QQT(CN)4], which can be converted from an ambipolar p-type-dominant to n-type semiconductor by either thermal annealing or direct laser writing.The chemical structure of the QQT(CN)4 oligomer is shown in the inset of Figure 1a. Quinoidal oligothiophene derivatives generally show a low highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy bandgap and are very promising candidates for n-type or single-component ambipolar organic FETs. [16][17][18][19][20][21] We have fabricated top-contact bottom-gate organic FETs under ambient conditions by spin-coating a QQT(CN)4 thin film on top of a polyimide gate-dielectric layer and using chromium drain/source electrodes. The transfer and output characteristics displayed in Figure 1 show that the device based on as-prepared QQT(CN)4 thin film exhibits an ambipolar behavior with a predominant hole-transport character. The charge-carrier field-effect mobilities were extracted from the transfer characteristics in the saturated regions. Hole and electron mobilities were measured to be 2 AE 1 Â 10 À3 and 4 AE 1 Â 10 À4 cm 2 V À1 s À1 , respectively. Compared to the QQT(CN)4-based device performance obtained using octadecyltrichlorosilane-treated SiO 2 as gate-dielectric layer and gold top-contact electrodes, [16] these mobility values are substantially lower. However, the use of a polyimide gate dielectric presents the significant advantage of strongly reducing COMMUNICATION www.advmat.de www.MaterialsViews.com

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