Hierarchically Assembled Counter Electrode for Fiber Solar Cell Showing Record Power Conversion Efficiency

Abstract Fiber solar cells have attracted significant interest as a promising wearable power supply solution for their merits of high flexibility, lightweight, and good compatibility with textile configuration and weaving process. However, because of the limited ion diffusion and charge transfer in the fiber counter electrode, the poor photovoltaic performances have long been one obstacle to hinder their real applications. Herein, in mimicking the efficient mass transport and exchange through the vascular tissue of plants like pine needle, a hierarchically assembled carbon nanotube (HCNT) fiber counter electrode is fabricated by a scalable process. The designed hierarchically aligned channels with large sizes of micrometers and small sizes of tens of nanometers in the HCNT fiber offers high‐flux pathways for rapid ion diffusion and abundant active area for charge transport, thus endowing the fiber dye‐sensitized solar cell with a record power conversion efficiency of 11.94%. By weaving such fiber solar cells in a scalable way, a flexible and breathable large photovoltaic textile (17 cm × 22 cm) is made to present a power output of 22.7 mW. These fiber solar cells are further integrated with fiber lithium‐ion batteries to efficiently power wearable electronics.