The semiconductor triboelectric nanogenerator (TENG) based on the tribovoltaic effect has the characteristics of direct current and high current density, but the energy transfer and conversion mechanism is not completely clear. Here, a series of gallium nitride (GaN)-based semiconductor direct-current TENGs (SDC-TENGs) are investigated for clarifying the carrier excitation and transport mechanism. During the friction process, the external output current always flows from GaN to silicon or aluminum, regardless of the direction of the built-in electric field, because of the semiconductor types. These results reveal that the carrier transport direction is dominated by the interfacial electric field formed by triboelectrification, which is also verified under different bias voltages. Moreover, the characteristics dependent on the frictional force have been systematically investigated under different normal forces and frictional modes. The open-circuit voltage and short-circuit current of SDC-TENG are both increased with a larger frictional force, which shows that the more severe friction results in both a larger interface electric field and more excited carriers. The maximum voltage can reach 25 V for lighting up a series of LEDs, which is enhanced by four times compared to the cutting-edge reported SDC-TENGs. This work has clarified the friction-dominated carrier excitation and transport mechanism for the tribovoltaic effect, which demonstrates the great potential of semiconductor materials for frictional energy recovery and utilization.

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The Ba(1−x)CaxZryTi(1−y)O3 (BCZT), a lead-free ceramic material, has attracted the scientific community since 2009 due to its large piezoelectric coefficient and resulting high dielectric permittivity. This perovskite material is a characteristic dielectric material for the pulsed power capacitors industry currently, which in turn leads to devices for effective storage and supply of electric energy. After this remarkable achievement in the area of lead-free piezoelectric ceramics, the researchers are exploring both the bulk as well as thin films of this perovskite material. It is observed that the thin film of this materials have outstandingly high power densities and high energy densities which is suitable for electrochemical supercapacitor applications. From a functional materials point of view this material has also gained attention in multiferroic composite material as the ferroelectric constituent of these composites and has provided extraordinary electric properties. This article presents a review on the relevant scientific advancements that have been made by using the BCZT materials for electric energy storage applications by optimizing its dielectric properties. The article starts with a BCZT introduction and discussion of the need of this material for high energy density capacitors, followed by different synthesis techniques and the effect on dielectric properties of doping different materials in BCZT. The advantages of thin film BCZT material over bulk counterparts are also discussed and its use as one of the constituents of mutiferroic composites is also presented. Finally, it summarizes the future prospects of this material followed by the conclusions.

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