Optimizing the Optical Properties of Tin Oxide Aerogels Through Defect Passivation

Tin oxide aerogels were synthesized using an epoxide-assisted technique and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, x-ray diffraction, and UV–Vis spectroscopy to study the effects of post-synthesis annealing and peroxide treatment. While bulk tin oxide exhibits an optical bandgap of 3.6 eV, its aerogel form often displays a larger apparent bandgap around 4.6 eV due to defects. Our study reveals that annealing decreases the optical bandgap, but is ineffective in removing defects. Conversely, peroxide passivation effectively lowers the bandgap and electronic disorder levels, suggesting that dangling bonds are the primary cause of the increased bandgap in tin oxide aerogels.