Metal–organic framework (MOF)-based electrolytes under gel/solid states have been widely used for electrochemical devices recently due to their designable metal centers/ligands and diffusion channels in the porous structures. Therefore, it is always desired to apply the MOF-based electrolytes in electrochromic (EC) fields. Yet, challenges exist in realizing their high optical transparency to satisfy the unique optical requirements of EC devices. Herein, a transparent MOF-based gel electrolyte (MGE) is demonstrated through the incorporation of 2-methylimidazole among MOF nanocrystals to prevent the strong light scattering of MOF nanocrystals. As a result, the gel electrolyte showed an improved average transmittance of ca. 82.2% compared with the MOF electrolytes without 2-methylimidazole (ca. 59.2%). In addition, because of the designed large channels in the porous MOF structure, the gel electrolyte exhibited a high ionic conductivity of 2.66 × 10–3 S cm–1. At last, we used the transparent MGEs to assemble two types (rigid and flexible) of quasi-solid-state EC devices based on inorganic WO3 and organic poly­(3,4-ethylenedioxythiophene) (PEDOT), respectively. Both devices showed great EC performances, and the flexible devices exhibited high mechanical stability under the bending state or even after being cut and punched, advancing the general applications of our transparent MGEs in EC fields.

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A novel high breakdown voltage (BV) AlGaN/GaN high-electron mobility transistor (HEMT) with a high-K/low-K compound passivation layer is proposed. The compound passivation layer is formed by blocks of low-K dielectric (Si 3 N 4) embedded in a high-K passivation layer (La 2 O 3). Owing to their different dielectric constants, there is a discontinuity of the horizontal electrical field at the high-K/ low-K interface, which can introduce a new electric field peak in the nearby channel in the semiconductor and can also modulate the distribution of the electric field along the channel. Hence, enhancement of BV can be achieved. Compared to the typical field-plate structure, high-K/low-K passivation introduces no parasitic capacitance. On the basis of the physical mechanism, several design principles for the high-K/low-K passivation layer are presented. Numerical simulation demonstrates a BV of 1400 V for the proposed device with four blocks of low-K dielectric embedded in a high-K passivation, compared to the BVs of 917 and 288 V for the device with high-K passivation and the device with low-K passivation, respectively.