Influence of carbon nanotubes on the optical properties of plasticized solid polymer electrolytes

•Optical properties were investigated doped polymer films in the wavelength range of 200-400 nm.•A energy gaps and band edge values shifted to lower energies on doping.•LiPF6, EC and CNT are responsible for the formation of defects in polymer electrolytes.•Increase in the degree of disorder in the films.

Polyethylene oxide (PEO) based solid polymer electrolyte films complexed with lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC) and carbon nanotubes (CNTs) are prepared by solution-casting technique. The complexation of doping materials with polymer is confirmed by X-ray diffraction and infrared studies. The incorporation of LiPF6, EC and CNTs into the host polymer shows a significant increase in conductivity of 10−10 and 10−3 S cm−1. The optical properties such as direct and indirect band gaps are investigated for pure and doped polymer films within a wavelength range of 200-400 nm. It is found that the energy gaps and band edge values shift towards lower energies upon doping. It is shown that LiPF6, EC and CNTs are responsible for the formation of defects in polymer electrolytes, which increases the degree of disorder in the films.

Graphical abstractOptical band decrease from 5.92 to 4.60 eV for direct optical band gap and from 5.70 to 4.42 eV for indirect optical band gap. Decrease in the band gap is caused by an alloying effect such as LiPF6, EC and CNT.Download full-size image