All‐Dry Fabricated Core–Sheath Carbon Nanotube Yarn Electrode for Fiber‐Shaped Dye‐Sensitized Solar Cells

Conventional fiber‐shaped dye‐sensitized solar cells (FDSSCs) that use platinum (Pt) as the counter electrode (CE) suffer from high costs and material scarcity, which significantly limit their practical applicability. Herein, a novel core–sheath carbon nanotube (CNT) yarn (CSCNY) is developed by coating a CNT film onto a multi‐ply twisted CNT yarn using a facile dry mechanical process and is applied as the CE in a flexible solid‐state FDSSC. The CSCNY maintains the coiled morphology of the fiber while minimizing entanglement by eliminating internal tension. Additionally, the smooth surface morphology of the CNY reduces the number of interfacial voids with the photoelectrode, thereby facilitating charge transport and ion diffusion. Electrochemical analyses confirm that the CSCNY electrode exhibits enhanced electrocatalytic activity toward the I − /I 3 − redox couple. Consequently, the CSCNY‐based FDSSC achieves a maximum power conversion efficiency of 6.25%, surpassing that of its conventional Pt‐based counterparts, owing to the enhanced open‐circuit voltage and fill factor. Furthermore, the device retains over 80% of its initial efficiency after 450 stretching‐bending cycles, demonstrating superior mechanical durability and long‐term operational stability, even after >200 h of operation. These findings highlight the potential of CSCNY as an effective and scalable alternative to Pt CEs in flexible FDSSCs.