In this 2D NiCo-MOF/rGO hybrid, the MOF nanosheets provide abundant active sites while the conductive rGO provide rapid electron transport.

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Due to the advantages of being light, conformable, nonfragile, and bendable, flexible electronic devices have been considered for various applications such as flexible displays, bendable memories, e-textiles, radio frequency identifications (RFIDs), artificial skin/muscles, and wearable electronics. [1,2] Compared to rigid devices, the main challenges of flexible devices are finding suitable materials and fabrication methods to overcome the inherent barrier of low glass-transition temperature (T g ) for flexible substrates.Organic small molecules and polymers are flexible, but the corresponding devices are subject to issues resulting from short lifetime and difficult packaging. Conventional hydrogenated amorphoussilicon (a-Si:H) thin-film transistors (TFTs) can be prepared on flexible plastic substrates due to the low processing temperature of plasma-enhanced chemical vapor deposition (PECVD) (<200 C). [3] However, reduced carrier mobility and unstable characteristics under gate-bias stress limit their applications in flexible electronics. [4] Although low-temperature polysilicon (LTPS) TFTs show high mobility and stable characteristics, they are still unsuitable for flexible devices due to the crystallization temperature of polysilicon being higher than the T g of plastic substrates. [5,6] In addition, nanocrystalline-silicon (nc-Si) TFTs can show both good device stability and high carrier mobility (>10 2 cm 2 V À1 s À1 ). However, their high cost is a huge obstacle for industrial production, and the growth rate of nc-Si still requires further enhancement.Transparent oxide semiconductors (TOSs) have attracted considerable research interest because of their superior controllability in carrier generation and excellent optical transparency in the whole visible region. TFTs based on TOSs, such as InGaZnO, GaSnZnO, and AlSnZnInO, have been intensively studied due to the lower processing temperature than nc-Si TFTs, better uniformity than LTPS TFTs, and higher mobility and better stability than a-Si:H TFTs. [7][8][9] Among the state-of-the-art semiconductor materials, amorphous InGaZnO (a-IGZO), which was first fabricated by Nomura et al. in 2003, [10] is one of the most promising options, with an a-IGZO TFT successfully prepared on a flexible polyethylene terephthalate (PET)

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Pentacene organic thin-film transistors (OTFTs) using La x Nb (1Àx) O y as gate dielectric with different La contents (x ¼ 0.347, 0.648) have been fabricated and compared with those using Nb oxide or La oxide. The OTFT with La 0.648 Nb 0.352 O y as gate dielectric can achieve a high carrier mobility of 1.14 cm 2 V À1 s À1 (about 1000 times and 2 times those of the devices using Nb oxide and La oxide, respectively), and has negligible hysteresis of À0.130 V, small sub-threshold swing of 0.280 V/ dec, and low threshold voltage of À1.35 V. AFM and XPS reveal that La can suppress the formation of oxygen vacancies in Nb oxide while Nb can alleviate the hygroscopicity of La oxide, which results in a more passivated and smoother dielectric surface, leading to larger pentacene grains grown and thus higher carrier mobility. The OTFT with Nb oxide has an anticlockwise hysteresis but the device with La oxide shows an opposite direction. This can be explained in terms of donorlike traps due to oxygen vacancies and acceptor-like traps originated from hydroxyl ions formed after La 2 O 3 absorbing water moisture. V

Pentacene organic thin-film transistors (OTFTs) using La x Ta (1-x) O y as gate dielectric with different La contents (x = 0.227, 0.562, 0.764, 0.883) have been fabricated and compared with those using Ta oxide or La oxide. The OTFT with La 0.764 Ta 0.236 O y can achieve a carrier mobility of 1.21 cm 2 /V·s, which is about 40 times and two times higher than those of the devices using Ta oxide and La oxide, respectively. As supported by XPS, AFM and noise measurement, the reasons lie in that La incorporation can suppress the formation of oxygen vacancies in Ta oxide, and Ta content can alleviate the hygroscopicity of La oxide, resulting in more passivated and smoother dielectric surface and thus larger pentacene grains, which lead to higher carrier mobility.

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