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We report the fabrication and electrical properties of flexible (Ba0.7Sr0.3)TiO3(BST) thick films. Fluorophlogopite mica substrates enable the growth of high-quality BST films because of their high melting temperature and flexible functionality for both concave and convex curvatures. The BST films are flat with quite small roughness of 4.2 nm, and dense without any pores or cracks. The BST films show a small remanent polarization of 3.8 μC/cm2, a high dielectric constant of 1390 at 10 kHz, a small leakage current density of 2.2 × 10–3A/cm2at 200 kV/cm, and a dielectric tunability of 45%. The dielectric tunability is slightly higher for concave bending and is robust with respect to successive mechanical bending up to 10,000 cycles.

Innovative material design is one of the most plausible routes to sufficiently enhance triboelectric outputs for self-powered electronic devices. Herein, we reported a g-C3N4embedded P(VDF-TrFE) composite as a strong candidate for boosting the output power via simultaneous harvesting of mechanical and light energies. Visible light-responsive g-C3N4nanosheets are chemically bonded to the ferroelectric P(VDF-TrFE) polymer and increase the ferroelectric polarization and dielectric constant of the composite. Kelvin probe force microscopy and photoluminescence measurements reveal that the enhanced triboelectric output is related to the increased workfunction, the reduced recombination rate of electron-hole pairs, and the band bending-induced photocarrier movement. The up-poled g-C3N4@P(VDF-TrFE) composite-based photoactive triboelectric nanogenerator (PA-TENG) generates a power (power density) of 2.0 mW (0.125 mW/cm2) under a blue light illumination, which is 10 times larger than PA-TENG under a dark condition and 54 times larger than bare P(VDF-TrFE)-based TENG. The output power is continued for at least up to 1.5 months in ambient conditions and is enough to power light-emitting diodes, a thermo-hygrometer, and a digital watch, which would be quite useful for individuals in the dark underground. This work provides a novel approach to boost the triboelectric output via a coupling of photocarrier and ferroelectric dipole and a useful hint to realize self-powered small electronics for safety issues in dark environments like caves and tunnels.

In operandotechniques have emerged to elucidate the fundamental mechanism of triboelectrification via relevant physical quantity measurement during the physical contact of two materials. Here, a correlation between frictional heat and triboelectric charge is reported in a metal-polymer triboelectric nanogenerator through the in operandotemperature measurement. Fluorine-doped tin oxide (FTO) metal is slid back-and-forth under different contact pressures across polydimethylsiloxane (PDMS) polymers having different degrees of crosslinking, i.e., mixing ratio. Both the triboelectric charge and temperature variation increase and become saturated with different time-constants. Notably, the saturated triboelectric charge increases, while the saturated temperature decreases, with increasing mixing ratio. In contrast, both saturated triboelectric charge and temperature increase with increasing contact pressure. X-ray photoemission spectroscopy reveals that chemical bonds are modified inhomogeneously at the surface, and that charged materials are transferred from PDMS to FTO in accordance with the mixing ratio- and sliding time-dependent triboelectric charges. Frictional heat plays a distributive role in bond rupture and temperature variation, depending on the activation energy and frictional coefficient of PDMS. In operandotemperature variation measurement provides important information on the specific bonds for triboelectrification and detailed charge-transfer process during physical contact.