Organic electrochemical transistors (OECTs) hold promise for developing a variety of high‐performance (bio‐)electronic devices/circuits. While OECTs based on p‐type semiconductors have achieved tremendous progress in recent years, n‐type OECTs still suffer from low performance, hampering the development of power‐efficient electronics. Here, it is demonstrated that fine‐tuning the molecular weight of the rigid, ladder‐type n‐type polymer poly(benzimidazobenzophenanthroline) (BBL) by only one order of magnitude (from 4.9 to 51 kDa) enables the development of n‐type OECTs with record‐high geometry‐normalized transconductance (gm,norm ≈ 11 S cm−1) and electron mobility × volumetric capacitance (µC* ≈ 26 F cm−1 V−1 s−1), fast temporal response (0.38 ms), and low threshold voltage (0.15 V). This enhancement in OECT performance is ascribed to a more efficient intermolecular charge transport in high‐molecular‐weight BBL than in the low‐molecular‐weight counterpart. OECT‐based complementary inverters are also demonstrated with record‐high voltage gains of up to 100 V V−1 and ultralow power consumption down to 0.32 nW, depending on the supply voltage. These devices are among the best sub‐1 V complementary inverters reported to date. These findings demonstrate the importance of molecular weight in optimizing the OECT performance of rigid organic mixed ionic–electronic conductors and open for a new generation of power‐efficient organic (bio‐)electronic devices.

Conducting polymers, such as the p-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), have enabled the development of an array of opto- and bio-electronics devices. However, to make these technologies truly pervasive, stable and easily processable, n-doped conducting polymers are also needed. Despite major efforts, no n-type equivalents to the benchmark PEDOT:PSS exist to date. Here, we report on the development of poly(benzimidazobenzophenanthroline):poly(ethyleneimine) (BBL:PEI) as an ethanol-based n-type conductive ink. BBL:PEI thin films yield an n-type electrical conductivity reaching 8 S cm−1, along with excellent thermal, ambient, and solvent stability. This printable n-type mixed ion-electron conductor has several technological implications for realizing high-performance organic electronic devices, as demonstrated for organic thermoelectric generators with record high power output and n-type organic electrochemical transistors with a unique depletion mode of operation. BBL:PEI inks hold promise for the development of next-generation bioelectronics and wearable devices, in particular targeting novel functionality, efficiency, and power performance.

Solution-processed semiconducting transition metal dichalcogenides (TMDs) are at the centre of an ever-increasing research effort in printed (opto)electronics. However, device performance is limited by structural defects resulting from the exfoliation process and poor inter-flake electronic connectivity.Here, we report a new molecular strategy to boost the electrical performance of TMD-based devices via the use of dithiolated conjugated molecules, to simultaneously heal sulfur vacancies in solutionprocessed transition metal disulfides (MS2) and covalently bridge adjacent flakes, thereby promoting percolation pathways for the charge transport. We achieve a reproducible increase by one order-ofmagnitude in field-effect mobility (µFE), current ratios (ION / IOFF), and switching times (τS) of liquid-gated transistors, reaching 10 -2 cm 2 V -1 s -1 , 10 4 , and 18 ms, respectively. Our functionalization strategy is an universal route to simultaneously enhance the electronic connectivity in MS2 networks and tailor on demand their physicochemical properties according to the envisioned applications.

including graphene, [10,[13][14][15][16] carbon nanotubes (CNTs), [5,17] conductive elastomers, [4,18] silicon nanowires and nanostrips, [19] and metal nanowires and nanoparticles. [20] Among them, graphene has been the most studied due to its excellent electrical conductivity, [21] high transmittance, [22] outstanding mechanical properties, [23] and large surface area. [24,25] It is noteworthy that graphene can be safely employed in devices being in direct contact with human skin, enabling applications as tattoo sensors. [26] To evaluate the performance of a pressure sensor, several parameters need to be taken into account such as sensitivity, response time, detection limit, linearity range, cyclability, power consumption, and robustness. The sensitivity of the pressure sensor, defined as the ratio between the change in the electrical signal output and the applied pressure, is probably the most important figure-of-merit of the sensor. Sensors featuring high sensitivities are capable of detecting extremely small changes in the pressure, and can be exploited even to transduce muscle movements [16,27] as well as the subtle vibrations of sound [6,11,28,29] into electrical outputs. Compared to the complicated fabrication methods such as microelectromechanical systems [30,31] and microfluidics techniques, [7] the engineering of the structure of active material represents the simplest and the most straightforward approach for the fabrication of pressure sensors in which a small applied pressure can determine subtle structural changes in the electroactive material. For example, upon applying a pressure, cracks and structural defects can be generated, which results in modification of the percolation pathways for charge transport, and can ultimately result in large variations in the electrical output. [13,32,33] Moreover, the contact resistance at the electrode-active layer interface can be modulated by pressure resulting into an improvement of the sensitivity. [12,18,34,35] By using such a strategy, Suh and coworkers. [35] demonstrated a strain-gauge sensor, which is based on two interlocked arrays of Pt-coated polyurethane acrylate nanofibers supported on thin poly(dimethylsiloxane) layers. Furthermore, a change in capacitance can be induced by pressure, which is the working principle of capacitive pressure sensor. In that case the sensitivity can be improved by microstructurationThe development of pressure sensors is crucial for the implementation of electronic skins and for health monitoring integrated into novel wearable devices. Tremendous effort is devoted toward improving their sensitivity, e.g., by employing microstructured electrodes or active materials through cumbersome processes. Here, a radically new type of piezoresistive pressure sensor based on a millefeuille-like architecture of reduced graphene oxide (rGO) intercalated by covalently tethered molecular pillars holding on-demand mechanical properties are fabricated. By applying a tiny pressure to the multilayer structure, the electron tunnelling ruling th...