The defect passivation of perovskite films is an efficacious way to further boost the power conversion efficiency (PCE) and long-term stability of perovskite solar cells (PSCs). In this work, ionic liquids (ILs) of 1-butyl-2,3-dimethylimidazolium chloride ([BMMIm]Cl) are used as a modification layer in perovskite films in carbon-based CsPbBr 3 PSCs without a hole-transporting material (HTM) for passivating the surface defects. The preliminary results demonstrate that the [BMMIm]Cl modifier passivates the surface defects of the perovskite film and reduces the valence band of perovskite close to the work function of the carbon electrode, which causes a remarkably inhibited nonradiative and radiative charge recombination, improved energy-level matching, and decreased energy loss. After optimization, a champion efficiency of 9.92% with a V oc as high as 1.61 V is achieved for the [BMMIm]Cl tailored carbon-based CsPbBr 3 PSC without HTM, which is improved by 61.3% in comparison with 6.15% for the control device. Furthermore, the encapsulation-free PSC presents good longterm stability after storage in an air atmosphere with 70% RH at 20 °C or 0% RH at 80 °C as well as under continuous illumination conditions for 30 days. The significantly improved PCE and stability in high humidity or temperature suggest that the perovskite passivation by ILs is an effective strategy for fabricating high-PCE and stable PSCs.

Through passivating and promoting interfacial charge extraction, P3HT/ZnPc composite HTMs help CsPbBr3 PSC achieve a champion PCE of 10.03% and excellent stability.

The sodium dual ion battery (Na‐DIB) technology is proposed as highly promising alternative over lithium‐ion batteries for the stationary electrochemical energy‐storage devices. However, the sluggish reaction kinetics of anode materials seriously impedes their practical implementation. Herein, a Na‐DIB based on TiSe2‐graphite is reported. The high diffusion coefficient of Na‐ions (3.21×10−11–1.20×10−9 cm2 s−1) and the very low Na‐ion diffusion barrier (0.50 eV) lead to very fast electrode kinetics, alike in conventional surface capacitive storage systems. In‐situ investigations reveal that the fast Na‐ion diffusion involves four insertion stage compositions. A prototype cell shows a reversible capacity of 81.8 mAh g−1 at current density of 100 mA g−1, excellent stability with 83.52 % capacity retention over 200 cycles and excellent rate performance, suggesting its potential for next‐generation large scale high‐performance stationary energy storage systems.

An ideal network window electrode for photovoltaic applications should provide an optimal surface coverage, a uniform current density into and/or from a substrate, and a minimum of the overall resistance for a given shading ratio. Here we show that metallic networks with quasi-fractal structure provides a near-perfect practical realization of such an ideal electrode. We find that a leaf venation network, which possesses key characteristics of the optimal structure, indeed outperforms other networks. We further show that elements of hierarchal topology, rather than details of the branching geometry, are of primary importance in optimizing the networks, and demonstrate this experimentally on five model artificial hierarchical networks of varied levels of complexity. In addition to these structural effects, networks containing nanowires are shown to acquire transparency exceeding the geometric constraint due to the plasmonic refraction.

Perovskite solar cells (PSCs) are being rapidly developed at a fiery stage due to their marvelous and fast-growing power conversion efficiency (PCE). Advantages such as high PCE, solution processability, tunable band gaps, and flexibility make PSCs one of the research hot spots in the energy field. Flexible PSCs (f-PSCs) owing to high power-to-weight ratios can be promising candidates to serve as power sources in mobile energy systems, space energy systems, portable functional devices, and so on. Herein, we give a review on recent progress in f-PSCs involving flexible substrates and flexible transparent electrodes, performance enhancement by optimizing functional layers, large-scale fabrication techniques, flexibility promotion strategies, and their potential applications. Furthermore, perspectives are discussed on the future development of f-PSCs.