This study investigates the effect of co-doping with nanographene on the properties of FTO layers produced by spray pyrolysis. The results show that co-doping with nanographene enhances phase separation processes within the bulk of the FTO layer. The inhomogeneities formed during phase separation are depleted of fluorine compared to the film bulk. Co-doping with nanographene also significantly modifies the optical properties of the FTO layers. Specifically, it alters the position and intensity of the peaks in the reflection spectra, indicating a change in the nature of the absorbing centers. Furthermore, the optical bandgap of the FTO layers decreases with an increasing degree of nanographene doping. Finally, co-doping with nanographene reduces the resistance of the FTO layers, which can be attributed to an increase in charge carrier mobility.

This study examines the effect of graphene oxide nanoparticle (NGO) doping (0.12–0.24 mol%) on the properties of FTO layers obtained by spray pyrolysis. The results show that nanographene promotes phase separation within the FTO bulk. The resulting inhomogeneities are fluorine-depleted relative to the surrounding film. NGO doping also modifies the position and intensity of peaks in the absorption spectra, indicating a change in the nature of the absorbing centers. The optical bandgap of the FTO layers decreases with the increase in NGO from 4.4 eV (undoped samples) to 3.95 eV (samples with the highest NGO concentration). Furthermore, NGO doping reduces the sheet resistance of the FTO layers. This reduction is attributed to increased charge carrier mobility resulting from passivation of nanocrystallite interfaces by graphene oxide nanoparticles. However, the sheet resistance depends non-monotonically on NGO content, with the lowest value observed at 0.16 mol% NGO. The increase in resistance at higher NGO concentrations is due to enhanced carrier scattering caused by the growing size and number of the phase inhomogeneities within the FTO layer.