The booming market of portable and wearable electronics has aroused the requests for advanced flexible selfpowered energy systems featuring both excellent performance and high safety. Herein, we report a safe, flexible, self-powered wristband system by integrating high-performance zinc-ion batteries (ZIBs) with perovskite solar cells (PSCs). ZIBs were first fabricated on the basis of a defective MnO 2−x nanosheetgrown carbon cloth (MnO 2−x @CC), which was obtained via the simple lithium treatment of the MnO 2 nanosheets to slightly expand the interlayer spacing and generate rich oxygen vacancies. When used as a ZIB cathode, the MnO 2−x @CC with a ultrahigh mass loading (up to 25.5 mg cm −2 ) exhibits a much enhanced specific capacity (3.63 mAh cm −2 at current density of 3.93 mA cm −2 ), rate performance, and long cycle stability (no obvious degradation after 5000 cycles) than those of the MnO 2 @CC. Importantly, the MnO 2−x @CC-based quasi-solid-state ZIB not only achieves excellent flexibility and an ultrahigh energy density of 5.11 mWh cm −2 (59.42 mWh cm −3 ) but also presents a high safety under a wide temperature range and various severe conditions. More importantly, the flexible ZIBs can be integrated with flexible PSCs to construct a safe, selfpowered wristband, which is able to harvest light energy and power a commercial smart bracelet. This work sheds light on the development of high-performance ZIB cathodes and thus offers a good strategy to construct wearable self-powered energy systems for wearable electronics.

Perovskite solar cells (PSCs) have achieved remarkable progress with high power conversion efficiency (PCE) and low cost. However, there is still huge room for improvement in terms of long-term stability,...

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SnO 2 has been the most commonly used electron transport layer (ETL) in perovskite solar cells (PSCs) due to its excellent electron mobility and stability. To meet the applications of SnO 2 ETL in large-scale solar cells, a rapid but inexpensive synthesis of high-quality SnO 2 film is urgently needed. Herein, SnO 2 quantum dots (QDs) were synthesized through a super rapid (∼3 min), additive-free microwave-assisted reaction. Comparing with the crystalized SnO 2 films, the small-sized SnO 2 QDs present improved electronic properties, including the Fermi level, conductivity, electron mobility, and trap density. Hence, with this SnO 2 ETL, the power conversion efficiency of the PSCs reached 20.24% using a CH 3 NH 3 PbI 3 absorber, which is among the highest values in the same rank. Overall, these results demonstrate a bright future for the facile microwave-assisted synthesis of SnO 2 QDs along with their application for highly flexible and efficient PSCs.

The development of solid-state electrolytes (SSEs) for high energy density lithium metal batteries (LMBs) usually needs to take into account of the interfacial compatibility against lithium metal and the electrolyte stability suitable for a high-potential cathode. In this study, through a facile two-step coating process, novel double-layer solid composite electrolytes (SCEs) with Janus characteristics are customized for the high-voltage LMBs with improved room-temperature cycling performance. Among which, high-voltage resistant poly­(vinylidene fluoride) (PVDF) is adopted here for the construction of an electrolyte layer facing the cathode, while the other layer against the lithium anode is composed of the polymer matrix of poly­(ethylene oxide) (PEO) blended with PVDF to obtain a lithium metal-friendly interface. With the further incorporation of Laponite clay, the PVDF/(PEO+PVDF)-L SCEs not only exhibit improved mechanical properties, but also achieve a highly increased ionic conductivity (5.2 × 10–4 S cm–1) and lithium ion migration number (0.471) at room temperature. The assembled NCM523|PVDF/­(PEO+PVDF)-L SCEs|Li cells thus are able to deliver the initial discharge capacity of 153.9 mAh g–1 with 80.8% capacity retention after 200 cycles at 0.3 C. Such easily manufactured double-layer SCEs capable of operating steadily at room temperature provide a competitive electrolyte option for high-voltage solid-state LMBs.

Exfoliation of bulk materials is an efficient approach for the fabrication of two-dimensional nanomaterials, whereas the applications of the method are mostly limited to the delamination of materials with weak...

Although perovskite solar cells (PSCs) have exhibited a high-power conversion efficiency, the reproducibility of high-quality perovskite films is still a big challenge for large-scale flexible devices. One reason is the super narrow antisolvent dripping window, the other one is the difficulty in controlling the secondary phases. Herein, 18C6 is introduced into the perovskite precursor to achieve a high-quality and reproducible large-scale (7 Â 7 cm 2) flexible perovskite film by enlarging the antisolvent dripping window from 2 to 20 s, with an average efficiency of 13.33% (best 15.80%). Moreover, from the in situ grazing-incidence wide-angle X-ray scattering result, the 2H phase perovskite is highly suppressed with the additive of 18C6. The generality of the approach is also demonstrated in other antisolvents such as ethyl acetate. This finding provides an innovative solution to the realization of repeatable, large-scale solution fabrication of PSCs.

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