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In polymer dielectric energy storage, even polymers with high glass transition temperatures suffer significant degradation in energy storage performance as temperature increases, primarily due to a sharp rise in electrical conduction loss. In this study, we employ atomic layer deposition to coat the surface of a PEI/PVDF blend film with an Al2O3inorganic layer to enhance its energy storage performance at high temperatures. The influence of the inorganic layer's thickness on high-temperature energy storage performance is thoroughly analyzed. Experimental results and finite element simulations demonstrate that an ultra-thin Al2O3inorganic layer with the thickness of 50 nm effectively reduces leakage current density and mitigates space charge accumulation within the PEI/PVDF blends, thereby improving the high-temperature energy storage performance of the blends. Notably, under an applied electric field of 500 MV/m at 150 °C, the PEI/PVDF blend film with 50 nm Al2O3layer achieved a discharge energy density of 5.45 J/cm3and a charge-discharge efficiency of 97.75 %.

The performance improvements of AlGaN‐based deep ultraviolet light‐emitting diodes (DUV‐LEDs) with multigradient electron blocking layer (EBL) and triangular last quantum barrier (LQB) are investigated. The results show that the maximum internal quantum efficiency (IQE) is improved by 44.9% and light output power (LOP) is improved by 58.1% at 200 A cm−2, exhibiting a tremendous improvement compared to the conventional structure. These improvements are mainly attributed to the fact that both multigradient EBL and triangular LQB can generate negative polarization charges in the graded composition layer, which leads to a significant increase in hole concentration compared to the conventional EBL and LQB structures. Meanwhile, the multigradient EBL can transform the conventional triangular barrier into an arc‐shaped barrier, increasing the electron potential barrier height and decreasing the hole potential barrier height. This unique design suppresses electron leakage and enhances hole injection, leading to a significant enhancement of the IQE and alleviation of the efficiency droop. The IQE and LOP improvements of AlGaN‐based deep ultraviolet light‐emitting diodes (DUV‐LEDs) with multigradient electron blocking layer (EBL) and triangular last quantum barrier (LQB) are mainly attributed to generating negative polarization charges in the graded composition layer. Consequently, the proposed EBL and LQB significantly increase hole concentration compared to the conventional structures.

Numerical simulation results reveal that introducing polarization-induced doping hole injection layer (HIL) in the DUV-LEDs results in a downward band-bending at the EBL/HIL interface, which causes more severe electron leakage. The effect of optimizing EBL thickness on the performance of DUV-LEDs was investigated to mitigate the side-effects due to the introduction of polarization-induced doping HIL. The experimental results show that as the EBL thickness increases, the external quantum efficiency (EQE) and wall-plug efficiency (WPE) of the DUV-LEDs increase and then decrease, while the efficiency droop in an opposite trend. The maximum EQE and WPE of 5.95% and 5.48%, respectively, were achieved when the EBL thickness was 20 nm. Meanwhile, increasing the EBL thickness can improve the DUV-LED reliability. However, an excessively thick EBL will deteriorate the reliability due to generating more Joule heat. Therefore, the reliability of DUV-LED was optimal when the EBL thickness was 25 nm.