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The electron‐transport layer (ETL) plays an important role in the photovoltaic performance of perovskite solar cells (PSCs), and the energy level match of functional layers can appreciably improve the power conversion efficiency (PCE) of PSCs. Herein, we choose the rare‐earth europium ion Eu3+ to dope a mesoporous TiO2 ETL. X‐ray diffraction, field‐emission scanning electron microscopy, ultraviolet photoelectron spectroscopy, time‐resolved photoluminescence, and incident‐photo‐to‐current conversion efficiency experiments were performed to characterize the material. It is found that the Eu doping does not change the morphology, grain size, and crystallinity of TiO2. However, Eu doping upshifts the Fermi level of TiO2 ETL by scavenging oxygen atoms and introducing oxygen vacancies on the surface of the layer, which results in low series resistance and fast charge transport in the ETLs, which in turn increases the power conversion efficiency of the device from 15.85 % (undoped PSC) to 17.90 % (Eu‐doped PSC). This work demonstrates an effective approach for enhancing the performance of PSCs by rare‐earth doping.

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NiTe/NiSe composites grown in situ on Ni foam are successfully developed as a binder‐free electrode for supercapacitors. The as‐obtained NiTe/NiSe composite electrode exhibits excellent electrochemical properties with a higher specific capacitance of 1868 F g−1 (5.60 F cm−2) at a current density of 1 A g−1. In addition, an asymmetric supercapacitor is fabricated with NiTe/NiSe as the positive material and active carbon (AC) as the negative material. The resulting NiTe/NiSe//AC device exhibits a high energy density of 33.7 Wh kg−1 at a power density of 800 W kg−1, providing good cycling performance that retained 86.2 % of the initial capacitance at 2 A g−1 after 5000 cycles. All of the results illustrate that the NiTe/NiSe electrode is promising for potential application in supercapacitors and other fields.

A rod‐like hollow cobalt tungstate/non‐stoichiometric cobalt sulfide (CoWO4/Co1−xS) hybrid is successfully grown in situ on nickel foam through a simple two‐step hydrothermal process. Owing to the unique hollow structure, the as‐synthesized CoWO4/Co1−xS hybrid electrode possesses a large surface area and delivers a high specific capacitance of 1894.5 F ⋅ g−1 at a current density of 1 A ⋅ g−1. By using the CoWO4/Co1−xS hybrid electrode as the anode and an activated carbon (AC) electrode as the cathode, an asymmetric supercapacitor of CoWO4/Co1−xS//AC exhibits a high capacitance of 103.1 F ⋅ g−1 and high specific capacitance retention of 87.27 % after 5000 cycles. Furthermore, the asymmetric supercapacitor demonstrates a maximum power density of 4000 W ⋅ kg−1 at an energy density of 22.5 Wh ⋅ kg−1. The superior performance of the device can be ascribed to distinctive structure and positive synergistic effects in the hybrid. The facile preparation process and excellent performance presented here indicate the CoWO4/Co1−xS hybrid to be a promising candidate electrode material for supercapacitor applications.