Performance modulation of contact electrification nanogenerators by controlling the doping concentration of fluorine-doped tin oxide

Contact electrification nanogenerators (CENGs) were fabricated, and their output performance was modulated by controlling the doping concentration of fluorine-doped SnO₂ (FTO) thin films. As the fluorine source content was increased from 0.8 to 1.2 mM during spray pyrolysis deposition, the electron concentration in the FTO thin film increased from 1.84 × 10²⁰ to 5.22 × 10²⁰ cm⁻³, which is much larger than the Mott critical carrier concentration of SnO₂. The output voltage and current from the CENGs which were fabricated by the aluminium and FTO surfaces increased from 2.76 to 5.66 V and from 0.003 to 0.005 μA/cm² when controlling the electron concentration in the FTO layer from 5.22 to 1.84 × 10²⁰ cm⁻³. The modulation of the output performance of the CENGs originated from the change in work function of the FTO layer by Burstein-Moss shift.