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CNT yarn-based supercapacitors 265

Fig. 10.11 (A) SEM image of the threadlike integrated energy wire, consisting of photo-
electric conversion (PC) and energy storage, at the PC end. (B) Photograph of the entire
integrated threadlike device. (C) SEM image of the ES at the ES end. (D) Photocharging-
discharging curve of the threadlike integrated energy wire. The discharging current is
0.1 μA. (Reproduced with permission from T. Chen, L. Qiu, Z. Yang, Z. Cai, J. Ren, H. Li, H. Lin,
X. Sun, H. S. Peng, Angew. Chem. Int. Ed. 51 (2012) 11977–11980.)

wire, after coating with electrolytes, as the top electrode for the solar cell
(Fig. 10.11A and B) and SC (Fig. 10.11C). As shown in Fig. 10.11D, the
SC in this integrated device was rapidly charged up to a voltage close to
the open-circuit voltage of the DSSC upon light irradiation. Entire energy
conversion and storage efficiency was up to 1.5%. Zhang et al. developed
a coaxial self-powered “energy fiber” containing a polymer solar cell and
an SC based on CNTs [97]. The “energy fiber” integrates the functions of
photovoltaic conversion and energy storage elements in series on a com-
mon modified Ti wire.

10.6 Potential applications and future directions

The unique merits of threadlike supercapacitors, including quick power deliv-
ery, superior low-temperature operation, lightweight, flexibility, and the abil-
ity to handle up to a million cycles, make them a strong candidate for various
wearable electronics, smart clothes, electronic skins, and implantable medical
devices. This chapter reviewed recent progress in charge storage mechanisms,