Future renewable energy supplies and a sustainable environment rely on many important catalytic processes. Single‐atom catalysts (SACs) are attractive because of their maximum atom utilization efficiency, tunable electronic structures, and outstanding catalytic performance. Of particular note, transition‐metal SACs exhibit excellent catalytic activity and selectivity for the oxygen reduction reaction (ORR)—an important half reaction in fuel cells and metal–air batteries as well as for portable hydrogen peroxide (H2O2) production. Although considerable efforts have been made on the synthesis of SACs for ORR, the regulation of the coordination environments of SACs and thus the electronic structures still pose a big challenge. In this review, strategies for manipulating the coordination environments of SACs are classified into three categories, including regulation of the center metal atoms, manipulation of the surrounding environment connecting to the center metal atom, and modification of the geometric configuration of the support. Finally, some issues regarding the future development of SACs for ORR are raised and possible solutions are proposed.

In this work, a simple and efficient method for the extraction of all the parameters of a solar cell from a single current-voltage (I-V) curve under the constant illumination level is proposed. With the help of the Lambert W function, the explicit analytic expression for I is obtained. By reducing the number of the parameters, the expression for I only depends on the ideality factor n, the series resistance R s , and the shunt resistance R sh. This analytic expression is directly used to fit the experimental data and extract the device parameters. This simple solar cell parameter extraction method can be directly applied for all kinds of solar cells whose I-V characteristics follow the single-diode model. The parameters of various solar devices including silicon solar cells, silicon solar modules, dye-sensitized solar cells, and organic solar cells with standalone, tandem, and multi-junction structures have been successfully extracted by using our proposed method.

Perovskite CsPbIBr2 is attracting ever‐increasing attention for carbon‐based, all‐inorganic solar cells, owing to its well‐balanced band gap and stability features. However, significant interfacial recombination of charge carriers in solar cells fabricated with this active layer, which is intrinsically associated with the unwanted conduction band misalignment between CsPbIBr2 and the commonly used TiO2 electron transport layer, has limited power conversion efficiency (PCE) values. Herein, we demonstrate successful conduction band alignment engineering at the TiO2/CsPbIBr2 heterojunction by modifying TiO2 with CsBr clusters. Such modification triggers a beneficial increase in the conduction band minimum (CBM) of TiO2 from −4.00 to −3.81 eV and decreases the work function from 4.11 to 3.86 eV, thus promoting favorable band alignment at the heterojunction, suppressing recombination, and improving extraction and transport of charge carriers. As a result, the carbon‐based, all‐inorganic CsPbIBr2 solar cells exhibit over 20 % enhancement in average PCE. The champion device achieves a PCE of 10.71 %, a record among pure CsPbIBr2‐based cells, open‐circuit voltage of 1.261 V, and excellent stability.

Inorganic halide perovskite CsPbIBr2 possesses the most balanced band gap and stability characters among all of the concerned analogs for carbon-based, all-inorganic solar cells that are free of any hole-transporting layers and noble-metal electrodes. Yet, the current CsPbIBr2 solar cells seem to deliver the lowest record efficiency. This is originally plagued by a serious energy loss (E loss) in the cells, which thus limits their open-circuit voltages (V oc) severely. Herein, we demonstrate a light-processing technology that can overcome this obstacle successfully, by enabling the full-coverage, pure-phase CsPbIBr2 films featured with large grains, high crystallinity, and preferential [100] grains orientation, along with favorable electronic structure. It is achieved by the exposure of CsPbIBr2 precursor film formed in a conventional one-step spin-coating route to a simulated AM 1.5 G illumination before thermal annealing. The resulting carbon-based, all-inorganic planar cells give an optimized power conversion efficiency (PCE) of 8.60% with the V oc of 1.283 V. Notably, such an impressive V oc stands the highest value among all of the previously reported CsPbIBr2 solar cells; hence, its PCE exceeds nearly all of them. Therefore, our work suggests a new route to further improve the efficiency of low-cost, stable, and simple-fabrication CsPbIBr2 solar cells.

Ultra-wide bandgap semiconductor Ga2O3 based electronic devices are expected to perform beyond wide bandgap counterparts GaN and SiC. However, the reported power figure-of-merit hardly can exceed, which is far below the projected Ga2O3 material limit. Major obstacles are high breakdown voltage requires low doping material and PN junction termination, contradicting with low specific on-resistance and simultaneous achieving of n- and p-type doping, respectively. In this work, we demonstrate that Ga2O3 heterojunction PN diodes can overcome above challenges. By implementing the holes injection in the Ga2O3, bipolar transport can induce conductivity modulation and low resistance in a low doping Ga2O3 material. Therefore, breakdown voltage of 8.32 kV, specific on-resistance of 5.24 mΩ⋅cm2, power figure-of-merit of 13.2 GW/cm2, and turn-on voltage of 1.8 V are achieved. The power figure-of-merit value surpasses the 1-D unipolar limit of GaN and SiC. Those Ga2O3 power diodes demonstrate their great potential for next-generation power electronics applications.