MXenes, an emerging class of two-dimensional (2D) transition metal carbides and nitrides, have potential for application as high-performance, low-cost electrodes in organic field-effect transistors (OFETs) because of their water dispersibility, high conductivity, and work-function tunability. In this study, we successfully fabricated a large-scale, uniform Ti3C2T x MXene electrode array on a flexible plastic substrate for application in high-performance OFETs. The work function of the Ti3C2T x MXene electrodes was also effectively modulated via chemical doping with NH3. The fabricated OFETs with Ti3C2T x MXene electrodes exhibited excellent device performance, such as a maximum carrier mobility of ∼1 cm2·V–1·s–1 and an on–off current ratio of ∼107 for both p-type and n-type OFETs, even though all the electrode and dielectric layers were fabricated on the plastic substrate by solution processing. Furthermore, MXene-electrode-based complementary logic circuits, such as NOT, NAND, and NOR, were fabricated via integration of p-type and n-type OFETs. The proposed approach is expected to expand the application range of MXenes to other OFET-based electronic devices, such as organic light-emitting displays and electronic skins.

MXenes, an emerging class of 2D transition metal carbides and nitrides with the general formula Mn+1XnTx (n = 1–4), have potential for application as floating gates in memory devices because of their intrinsic properties of a 2D structure, high density‐of‐states, and high work function. In this study, a series of MXene–TiO2 core–shell nanosheets are synthesized by deterministic control of the surface oxidation of MXene. The floating gate (multilayer MXene) and tunneling layer (TiO2) in a nano‐floating‐gate transistor memory (NFGTM) device are prepared simultaneously by a facile, low‐cost, and water‐based process. The memory performance is optimized via adjustment of the thickness of the oxidation layer formed on the MXene surface. The fabricated MXene NFGTMs exhibit excellent nonvolatile memory characteristics, including a large memory window (>35.2 V), high programming/erasing current ratio (≈106), low off‐current (<1 pA), long retention (>104 s), and cyclic endurance (300 cycles). Furthermore, synaptic functions, including the excitatory postsynaptic current/inhibitory postsynaptic current, paired‐pulse facilitation, and synaptic plasticity (long‐term potentiation/depression), are successfully emulated using the MXene NFGTMs. The successful control of MXene oxidation and its application to NFGTMs are expected to inspire the application of MXene as a data‐storage medium in future memory devices.

The physical and chemical properties of MXenes are strongly dependent on surface terminations; thus, the tailoring of surface functional groups in two-dimensional transition-metal carbides (MXenes) may extend the applicability of these compelling materials to a wider set of fields. In this work, we demonstrate the chemical modification of Ti3C2T x MXene via diazonium covalent chemistry and the subsequent effects on the electrical properties of MXene. The 4-nitrophenyl group was grafted onto the surface of MXene through a solid–liquid reaction, which was confirmed by various characterization methods, including X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, electron energy loss spectroscopy, atomic force microscopy, and transmission electron microscopy. The degree of modification of MXene is expediently tunable by adjusting the concentration of the diazonium salt solution. The work function of functionalized MXene is modifiable by regulating the quantity of grafted diazonium surface groups, with an adjustable range of around 0.6 eV. Further, in this study, the electrical properties of modified MXene are investigated through the fabrication of field-effect-transistor devices that utilize modified MXene as a channel material. It was demonstrated that with increasing concentration of 4-nitrophenyl groups grafted onto the surface the on/off current ratio of the modified MXene was improved to as much as 3.56, with a corresponding decrease in conductivity and mobility. The proposed approach of controlled modification of surface groups in Ti3C2T x may imbue Ti3C2T x with favorable electronic behaviors and demonstrate prospects for use in electronic field applications.

Poly(3,:poly(4-styrene sulfonate) (PEDOT:PSS) has demonstrated outstanding performance as a charge transport layer or an electrode in various electronic devices, including organic solar cells, organic lightemitting diodes, and organic field-effect transistors (OFETs). The electrical properties of these devices are affected by the contact properties at the PEDOT:PSS−semiconductor junction. In this research, we performed work function (WF) engineering of electrohydrodynamic (EHD)-jet-printed PEDOT:PSS and successfully used it as an electrode to fabricate high-performance OFETs and complementary logic circuits. Two types of PEDOT:PSS materials−one with a high WF (HWF, 5.28 eV) and the other with a low WF (LWF, 4.53 eV)−were synthesized and EHD-jet-printed. The WF of PEDOT:PSS was deterministically modulated by approximately 0.75 eV through simple mixing of the two synthesized PEDOT:PSS materials in various ratios. OFETs fabricated with HWF and LWF PEDOT:PSS electrodes showed excellent electrical properties, including the ON/OFF switching ratio higher than 10 7 and the highest carrier mobility greater than 1 cm 2 •V −1 •s −1 . Furthermore, the HWF and LWF PEDOT:PSS electrodes were integrated to fabricate complementary metal−oxide− semiconductor (CMOS) NOT, NOR, and NAND circuits.

Solution-based processing of two-dimensional (2D) nanomaterials is highly desirable, especially for the low-temperature large-area fabrication of flexible multifunctional devices. MXenes, an emerging family of 2D materials composed of transition metal carbides, carbonitrides, or nitrides, provide excellent electrical and electrochemical properties through aqueous processing. Here, we further expand the horizon of MXene processing by introducing a polymeric superdispersant for MXene nanosheets. Segmented anchor-spacer structures of a comb-type polymer, polycarboxylate ether (PCE), provide polymer grafting–like steric spacings over the van der Waals range of MXene surfaces, thereby reducing the colloidal interactions by the order of 10 3 , regardless of solvent. An unprecedented broad dispersibility window for Ti 3 C 2 T x MXene, covering polar, nonpolar, and even ionic solvents, was achieved. Furthermore, close PCE entanglements in MXene@PCE composite films resulted in highly robust properties upon prolonged mechanical and humidity stresses.