Conductive self-standing nanofiber fabric of fluorine-doped tin oxide prepared by electrospinning for use in flexible electronics

Abstract

To realize a conductive substrate with heat resistance and flexibility for the application to flexible electronics, we aimed to reduce the resistance of the fluorine-doped tin oxide (FTO) ceramic nanofiber (NF) non-woven fabrics produced by the electrospinning method. Using NH₄F and SnF₂ as the raw materials for fluorine doping, the structure and electrical properties of FTO-NF non-woven fabric were compared. The non-woven fabrics obtained in both solutions were several cm square made by NFs with a diameter of 150~800 nm, and all NFs consisted of nanoparticles with a diameter of about 20 nm. The resistivity of the FTO-NF fabric could be reduced to $5.19 ~\mathrm{\Omega \cdot cm}$ by the improvements such as adding tin isopropoxide and mixing without using water for a solvent without making a precursor of FTO so that the raw material is uniformly adsorbed on the polymer in the solution. By considering the space occupancy of the NFs in the fabric, the minimum net resistivity of the FTO-NF fabric was estimated to be $0.56 ~ \mathrm{\Omega \cdot cm}$. Since the obtained FTO fabric was brittle and cracked when bent, we made a prototype of a three-layer NF non-woven fabric composited with amorphous SiO₂ NFs. The sheet resistance was $6.4 ~\mathrm{k\Omega /sq}$, no cracks or breaks occurred even when wrapped around a glass rod with a diameter of 5 mm$\phi$, and the rate of increase in the resistance after 100 bends could be suppressed to 4.9%.