Smart fabrics that can harvest ambient energy and provide diverse sensing functionality via triboelectric effects have evoked great interest for next‐generation healthcare electronics. Herein, a novel borophene/ecoflex nanocomposite is developed as a promising triboelectric material with tailorability, durability, mechanical stability, and flexibility. The addition of borophene nanosheets enables the borophene/ecoflex nanocomposite to exhibit tunable surface triboelectricity investigated by Kelvin probe force microscopy. The borophene/ecoflex nanocomposite is further fabricated into a fabric‐based triboelectric nanogenerator (B‐TENG) for mechanical energy harvesting, medical assistive system, and wound healing applications. The durability of B‐TENG provides consistent output performance even after severe deformation treatments, such as folding, stretching, twisting, and washing procedures. Moreover, the B‐TENG is integrated into a smart keyboard configuration combined with a robotic system to perform an upper‐limb medical assistive interface. Furthermore, the B‐TENG is also applied as an active gait phase sensing system for instantaneous lower‐limb gait phase visualization. Most importantly, the B‐TENG can be regarded as a self‐powered in vitro electrical stimulation device to conduct continuous wound monitoring and therapy. The as‐designed B‐TENG not only demonstrates great potential for multifunctional self‐powered healthcare sensors, but also for the promising advancements toward wearable medical assistive and therapeutic systems.
How the interparticle tunnelling affects the charge conduction of self-assembled gold nanoparticles is studied by three means: tuning the tunnel barrier width by different molecule modification and by substrate bending, and tuning the barrier height by high-dose electron beam exposure. All approaches indicate that the metal-Mott insulator transition is governed predominantly by the interparticle coupling strength, which can be quantified by the room temperature sheet resistance. The Hubbard gap, following the prediction of quantum fluctuation theory, reduces to zero rapidly as the sheet resistance decreases to the quantum resistance. At very low temperature, the fate of devices near the Mott transition depends on the strength of disorder. The charge conduction is from nearest-neighbour hopping to co-tunnelling between nanoparticles in Mott insulators whereas it is from variable-range hopping through charge puddles in Anderson insulators. When the two-dimensional nanoparticle network is under a unidirectional strain, the interparticle coupling becomes anisotropic so the average sheet resistance is required to describe the charge conduction.
Two‐dimensional (2D) tin (Sn)‐based perovskites have recently received increasing research attention for perovskite transistor application. Although some progress is made, Sn‐based perovskites have long suffered from easy oxidation from Sn2+ to Sn4+, leading to undesirable p‐doping and instability. In this study, it is demonstrated that surface passivation by phenethylammonium iodide (PEAI) and 4‐fluorophenethylammonium iodide (FPEAI) effectively passivates surface defects in 2D phenethylammonium tin iodide (PEA2SnI4) films, increases the grain size by surface recrystallization, and p‐dopes the PEA2SnI4 film to form a better energy‐level alignment with the electrodes and promote charge transport properties. As a result, the passivated devices exhibit better ambient and gate bias stability, improved photo‐response, and higher mobility, for example, 2.96 cm2 V−1 s−1 for the FPEAI‐passivated films—four times higher than the control film (0.76 cm2 V−1 s−1). In addition, these perovskite transistors display non‐volatile photomemory characteristics and are used as perovskite‐transistor‐based memories. Although the reduction of surface defects in perovskite films results in reduced charge retention time due to lower trap density, these passivated devices with better photoresponse and air stability show promise for future photomemory applications.
The hysteresis effect and switchable photovoltaic phenomena in organo-metal halide perovskite have been observed in perovskite solar cells with certain structures and under certain measure conditions. These phenomena were favorably applied to resistive random-access memory and human-brain-mimicking devices, especially using photons as a reading or stress probe apart from using electrical probe. However, the mechanisms causing these effects are not fully understood. In this paper, the perovskite devices with different hole transporting layers, which have the work functions ranging from 5.9 to 3.7 eV, were fabricated and systematically characterized by current–voltage measurements and time-resolved photoresponse measurements. These measurements show that the switchable photovoltaic phenomena are highly related to the work function of the hole transporting layer. The interfacial electronic structures of perovskite and several materials were studied in details using X-ray and ultraviolet photoemission spectroscopy (XPS and UPS), suggesting that the switchable photovoltaic is extensively dependent on the strong band bending effect. Light-mediated XPS measurements reveals that the degree of band bending in the perovskite layer was manipulated by charge trapping/detrapping and hole-carrier accumulation. Based on the electrical measurements and band diagram, we propose a model that combines ion migration and charge trapping/detrapping processes to explain the switchable photovoltaic phenomena.
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