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Compared to electrochemical energy devices such as batteries and supercapacitors, dielectric film capacitors have greater power densities and faster charging and discharging rates and are the essential components in power electronics. [4][5][6] Dielectric polymers possess unique features in comparison to their ceramic counterparts, including high breakdown strength, low dielectric loss, facile preparation, and graceful failure mechanism, which make them the materials of choice for scalable high-energy-density capacitors. [7][8][9][10][11] More recently, there is an urgent demand for dielectric materials capable of operating efficiently at elevated temperatures, e.g., 150 °C, in advanced electronics, electrified vehicles, and aerospace power systems. However, dielectric polymers are limited to relatively low working temperatures. [11][12][13][14][15] For example, the operation temperature of biaxially oriented polypropylene (BOPP), the industrial benchmark dielectric polymer, is well below 105 °C under the applied electric fields. [15] A variety of innovative approaches, including the incorporation of wide bandgap inorganic fillers, [16][17][18] deposition of ceramic coatings onto polymer films, [19][20][21] addition of high-electronaffinity molecular semiconductors, [22] and utilization of multilayer-structured films, [23][24][25] have been developed to improve the high-temperature capacitive performance of dielectric polymers. While these approaches are effective in hindering electrical conduction and reducing energy loss at high fields and elevated temperatures, the energy densities of the current high-temperature dielectric composites are limited (below 4 J cm −3 in most cases) owing to relatively low dielectric constant (K) values of the fillers, such as ≈3.5-4 of SiO 2 and boron nitride nanosheets (BNNSs) [16,26] and ≈7.9-10 of Al 2 O 3 . [26] On the other hand, the direct introduction of high-K inorganic fillers, such as TiO 2 with a K of 110 (ref. [27]) and BaTiO 3 with a K of ≈3000 (ref. [28]), into dielectric polymers with the goal of increasing the energy density has yielded very high energy loss and largely reduced chargedischarge efficiency (η) with increasing applied field and temperature. [29,30] For instance, at an applied field of 400 MV m −1 , the η of the polyimide composites with 1 vol% BaTiO 3 nanofibers is only 55% at 150 °C versus 92% at 25 °C. [30] Herein, we present High-energy-density polymer dielectrics capable of high temperature operation are highly demanded in advanced electronics and power systems. Here, the polyetherimide (PEI) composites filled with the core-shell structured nanoparticles composed of ZrO 2 core and Al 2 O 3 shell are described. The establishment of a gradient of the dielectric constants from ZrO 2 core and Al 2 O 3 shell to PEI matrix gives rise to much less distortion of the electric field around the nanoparticles, and consequently, high breakdown strength at varied temperatures. The wide bandgap Al 2 O 3 shell creates deep traps in the composites and thus yields ...

Solar-blind ultraviolet (UV) photodetectors (PDs) have attracted tremendous attention in the environmental, industrial, military, and biological fields. As a representative III-nitride material, AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties, such as tunable wide bandgaps for intrinsic UV detection. In recent decades, a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection. As integrated optoelectronic technology advances, AlGaN-based focal plane arrays (FPAs) are manufactured and exhibit outstanding solar-blind imaging capability. Considering the rapid development of AlGaN detection techniques, this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs. First, the basic physical properties of AlGaN are presented. The epitaxy and p-type doping problems of AlGaN alloys are then discussed. Diverse PDs, including photoconductors and Schottky, metal–semiconductor–metal (MSM), p-i-n, and avalanche photodiodes (APDs), are demonstrated, and the physical mechanisms are analyzed to improve device performance. Additionally, this paper summarizes imaging technologies used with AlGaN FPAs in recent years. Benefiting from the development of AlGaN materials and optoelectronic devices, solar-blind UV detection technology is greeted with significant revolutions.

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The thermoelectric properties in graphene nanoribbons modulated with stub structures are studied using atomistic simulation of electron and phonon transport. The results show that the phonon transport is dramatically suppressed by the elastic scattering of the stub structure; while the thermopower S can be enhanced by a few times of magnitude. This leads to a strong enhancement of the figure of merit (ZT). Moreover, it is found that the enhancement of ZT can be effectively tuned by modulating geometric parameters of the stub and edge shapes, which offers an effective way to improve the thermoelectric performance of graphene nanoribbons.

The thermal transport properties by phonons in zigzag graphene nanoribbons with structural defects are investigated by using nonequilibrium phonon Green's function formalism. We find that the combined effect of the edge and local defect plays an important role in determining the thermal transport properties. In the limit T → 0, the thermal conductance approaches the universal quantum value 3κ(0)(κ(0) = π(2)k(B)(2)T/3h) even when structural defects are presented in graphene nanoribbons. The thermal transport shows a noticeable transformation from quantum to classical features with increasing temperature in the system. A suggestion to tune the thermal conductance by modulating structural defects and the ribbon width in graphene nanoribbons is presented.