Degradation of perovskite has been a big problem in all-solid-state perovskite solar cells, although many researchers mainly focus on the high efficiency of these solar cells. This paper studies the stability of CH 3 NH 3 PbI 3 films and finds that CH 3 NH 3 PbI 3 is sensitive to moisture. The degradation reaction is proposed according to UV-Vis spectra and XRD results. In order to improve the degradation of CH 3 NH 3 PbI 3 , we introduce aluminum oxide as a post-modification material into all-solid-state perovskite solar cells for the first time. UV-Vis spectra show that Al 2 O 3 modification could maintain the absorption of CH 3 NH 3 PbI 3 after degradation. XRD results reveal that Al 2 O 3 could protect perovskite from degradation. Moreover, the device post-modified by Al 2 O 3 has shown more brilliant stability than that without modification when exposed to moisture. EIS results and dark current illustrate that the modification increased interface resistance in the dark, indicating the restrained electron recombination process.

Na 0.72 [L i0.24 Mn 0.76 ]O 2 , with reversible anionic redox reaction (ARR) and Mn 3+ / Mn 4+ redox, delivers the highest energy density (700 Wh/kg, 270 mAh/g, 1.5-4.5 V) among all Na cathode materials reported to date, surprisingly showing suppressed phase transition and low-strain characteristics. Our findings break the traditional cognition that ARR could only help increase the capacity. It is demonstrated in this work that ARR also plays a key role in stabilizing the structure to induce an even higher capacity with low strain.

Minimal domains for maximum energy Dielectric capacitors are important electronic components that can store energy, at least for a short period of time. Pan et al . used phase-field simulations to help determine the right combination of bismuth iron oxide, barium titanium oxide, and samarium doping that is likely to generate a material with excellent dielectric properties (see the Perspective by Chu). The simulations guide a set of experimental measurements showing this system can produce a very high-energy storage by breaking down polar domains to the nanometer scale. These materials could be useful for high-power applications and to suppress failure. —BG

Amorphous and heterojunction materials have been widely used in the field of electrocatalytic hydrogen evolution due to their unique physicochemical properties. However, the current used individual strategy still has limited effects. Hence efficient tailoring tactics with synergistic effect are highly desired. Herein, the authors have realized the deep optimization of catalytic activity by a constructing crystalline–amorphous CoSe2/CoP heterojunction. Benefiting from the strong electronic coupling at the interfaces, the d‐band center of the material moves further down compared to its crystalline–crystalline counterpart, optimizing the valence state and the H adsorption of Co and lowering the kinetic barrier of hydrogen evolution reaction (HER). The heterojunction shows an overpotential of 65 mV to drive a current density of 10 mA cm−2 in the acidic medium. Besides, it also shows competitive properties in both neutral and basic media. This work provides inspiration for optimizing the catalytic activity through combining a crystalline and amorphous heterojunction, which can be implemented for other transition metal compound electrocatalysts.