Fine-tuning optical bandgap and dielectric properties through fluorine doping in SnO2 nanoparticles

Tin dioxide (SnO2) possesses remarkable optical and electrical properties and finds applications in a diverse array of devices, including supercapacitors, gas sensors, batteries, and solar cells. Enhancing SnO2's optoelectronic characteristics can substantially improve the functionality of devices incorporating this material. In this research endeavor, we synthesized tin oxide nanoparticles doped with fluorine (F-SnO2) using the modified sol-gel method. Our results underscore the affirmative impact of fluorine incorporation of SnO2's optoelectronic properties. Strikingly, this doping procedure left the morphology and structure of the nanoparticles untouched, but it did induce changes in particle size. Notably, the reduction in bandgap from 3.87 eV for SnO2 to 3.70 eV for F-SnO2 nanoparticles suggests the generation of new energy levels below the conduction band due to doping. Electrical transport assessments using impedance spectroscopy revealed the semiconducting behavior of the samples. The Nyquist diagram was instrumental in evaluating the role of grain and grain boundaries, and an equivalent circuit was employed for sample modeling. Conductivity showed temperature dependency, displaying Mott's variable range hopping conduction mechanism at lower temperatures and small polaron hopping at higher temperatures. Moreover, the introduction of fluorine ions leads to an increase in conductance and decrease the resistance.Dielectric analysis identified polarization as the main factor behind the dielectric loss tangent. The dielectric constant and tan delta show typical behavior by decreasing with increasing frequency. These observations align with the Maxwell-Wagner model. The dielectric loss coupled with high permittivity values, render F-SnO2 a promising compound for energy storage. These findings underscore the potential of F-SnO2 nanoparticles to enhance the performance of SnO2-based devices across a diverse spectrum of applications.