Photoelectrochemcial (PEC) properties of TiO2 nanorod arrays (TNRA) have been extensively investigated as they are photostable and cost-effective. However, due to the wide band gap, only the UV part of solar light can be employed by TiO2. To enhance the photoresponse of TNRA in the visible range, carbon dots (C dots) were applied as green sensitizer in this work by investigating the effects of C dot loading and length of TiO2 nanorod on the PEC properties of TNRA/C dot nanocomposites. As the C dot loading increases, the photocurrent density of the nanocomposites was enhanced and reached a maximum when the concentration of the C dots was 0.4 mg/mL. A further increase in the C dot concentration decreased the photocurrent, which might be caused by the surface aggregation of C dots. A compromise existed between charge transport and charge collection as the length of TiO2 nanorod increased. The incident photon to current conversion efficiency (IPCE) of the TNRA/C dot nanocomposites in the visible range was up to 1.2-3.4%. This work can serve as guidance for fabrication of highly efficient photoanode for PEC cells based on C dots.

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The advances of flexible electronics have raised demand for power sources with adaptability, flexibility, and multifunctionalities. Triboelectric nanogenerators are promising replacements for traditional batteries. Here, a highly soft skin‐like, transparent, and easily adaptable biomechanical energy harvester, based on a hybrid elastomer and with a polyionic hydrogel as the electrification layer and current collector, is developed. By harvesting the energy in human motion, the device generates an open‐circuit voltage of 70 V, a short‐circuit current density of 30.2 mA m−2, and a maximum power density of 2.79 W m−2 in a single‐electrode working mode. Further, it is demonstrated that the device can deliver power under bending, curling or by simple tapping when attached to human skin. In addition, the optimal counterpart of the polyionic layer with highest electronegativity difference is selected from a series of contact electrification materials based on a two‐electrode working mode, where a flexible device with the matching counterparts is investigated. Serving as ionic conductor and electrification layer, this polyionic material shows promising application in future development of self‐powered flexible electronics.

A flexible BCZT/PVDF-HFP composite-nanofiber based PTNG is developed. The uniform distribution of BCZT nanoparticles on the fiber surface significantly enhances the electrical properties, where the highest output is achieved when BCZT is prepared via the sol–gel method.

The advances in wearable/flexible electronics have triggered tremendous demands for flexible power sources, where flexible nanogenerators, capable of converting mechanical energy into electricity, demonstrate its great potential. Here, recent progress on flexible nanogenerators for mechanical energy harvesting toward self‐powered systems, including flexible piezoelectric and triboelectric nanogenerator, is reviewed. The emphasis is mainly on the basic working principle, the newly developed materials and structural design as well as associated typical applications for energy harvesting, sensing, and self‐powered systems. In addition, the progress of flexible hybrid nanogenerator in terms of its applications is also highlighted. Finally, the challenges and future perspectives toward flexible self‐powered systems are reviewed.

a trend. [22-27] Currently, self-powered technologies based on piezoelectric materials [28-32] and triboelectric nanogenerator [33-37] are two typical strategies to convert mechanical energy into electricity. Compared to piezoelectric nanogenerator, triboelectric nanogenerator is more suitable for energy harvesting, as it typically can provide much higher output voltage and current. [38-40] However, reports of using triboelectric nanogenerator for flexible sensors are still much less than those of piezoelectric based ones. [41] The typical method of using triboelectric nanogenerator for stress sensing involves difference of electrical signal output with different contact areas. [35,42,43] Therefore, human motion caused contact separations in the wearable triboelectric nanogenerator can result in electricity output and thus tactile sensing. [35] To better meet Recent advances in thin, soft skin-integrated electronics have brought many opportunities in the wearable technics. A simple platform with the functionality of self-powering for epidermal electronics is reported. These electronics can generate electricity from external mechanical stresses that associates with triboelectric effect, and therefore afford excellent performance in tactile sensing and energy harvesting. Combined advances in materials and mechanics of the skin-integrated electronics with high efficiency energy harvesting techniques, triboelectric nanogenerators (TENGs) in an epidermal format is realized for the first time. The dots-distributed electrode pattern allows these electronics exhibiting excellent flexibility and stretchability, distinguishing a broad range of pressures that are relevant to normal body motions. The electricity output of the epidermal device from simple finger tapping modes can achieve >60 V of voltage and >1 µA of current, which is sufficient to light up 15 small light-emitting diodes. Furthermore, the authors also report a 4 × 4 sensor array based on these TENGs, and demonstrate a skin-like electronics for real-time motion monitoring and tactile mapping.

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