Graphene oxide induced fabrication of pillared and double-faced polyaniline arrays with enhanced triiodide reduction capability

Recent progress on nanostructured carbon-based counter/back electrodes for high-performance dye-sensitized and perovskite solar cells

Dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs) favor minimal environmental impact and low processing costs, factors that have prompted intensive research and development. In both cases, rare, expensive, and less stable metals (Pt and Au) are used as counter/back electrodes; this design increases the overall fabrication cost of commercial DSSC and PSC devices. Therefore, significant attempts have been made to identify possible substitutes. Carbon-based materials seem to be a favorable candidate for DSSCs and PSCs due to their excellent catalytic ability, easy scalability, low cost, and long-term stability. However, different carbon materials, including carbon black, graphene, and carbon nanotubes, among others, have distinct properties, which have a significant role in device efficiency. Herein, we summarize the recent advancement of carbon-based materials and review their synthetic approaches, structure-function relationship, surface modification, heteroatoms/metal/metal oxide incorporation, fabrication process of counter/back electrodes, and their effects on photovoltaic efficiency, based on previous studies. Finally, we highlight the advantages, disadvantages, and design criteria of carbon materials and fabrication challenges that inspire researchers to find low cost, efficient and stable counter/back electrodes for DSSCs and PSCs.

Compact Assembly and Programmable Integration of Supercapacitors

Microsized supercapacitors (mSCs) with small volume, rapid charge-discharge rate, and ultralong cyclic lifetime are urgently needed to meet the demand of miniaturized portable electronic devices. A versatile self-shrinkage assembling (SSA) strategy to directly construct the compact mSCs (CmSCs) from hydrogels of reduced graphene oxide is reported. A single CmSC is only 0.0023 cm³ in volume, which is significantly smaller than most reported mSCs in fiber/yarn and planar interdigital forms. It exhibits a high capacitance of up to 68.3 F cm^-3 and a superior cycling stability with 98% capacitance retention after 25 000 cycles. Most importantly, the SSA technique enables the CmSC as the building block to realize arbitrary, programmable, and multi-dimensional integration for adaptable and complicated power systems. By design on mortise and tenon joint connection, autologous integrated 3D interdigital CmSCs are fabricated in a self-holding-on manner, which thus dramatically reduces the whole device volume to achieve the high-performance capacitive behavior. Consequently, the SSA technique offers a universal and versatile approach for large-scale on-demand integration of mSCs as flexible and transformable power sources.