Spray pyrolysis derived Ce-doped SnO2 nanoparticles-based thin films: Tailoring band gap and conductivity for energy and optoelectronic applications

Ce-doped SnO2 nanoparticle-based thin films with Ce concentrations of 0%, 1%, 3%, and 5% are successfully deposited on glass substrates using the spray pyrolysis method and systematically investigated for optoelectronic and sustainable energy applications. X-ray diffraction analysis confirmed that all films crystallize in the tetragonal rutile structure (JCPDS No. 41-1445) with space group P4₂/mnm, without any secondary phases, indicating successful incorporation of Ce into the SnO2 lattice. The crystallite size decreased from ~26 nm to ~18 nm with increasing Ce content, accompanied by increased microstrain and dislocation density. FESEM and AFM analyses revealed a transition toward finer, more uniform, and compact nanoparticle morphology with reduced surface roughness (Ra decreased from 5.68 nm to 1.76 nm). Optical studies showed high transparency (~85–92%) in the visible region, with a slight decrease upon doping and a red shift of the absorption edge. The optical band gap, determined using Tauc plots, decreased from 3.85 eV for pure SnO2 to 3.65 eV for SnO2:Ce (5%), attributed to defect states and oxygen vacancies induced by Ce incorporation. FTIR spectra confirmed the presence of characteristic Sn–O bonds (~620–670 cm-1) along with hydroxyl and adsorbed species, with slight variations due to doping. Hall effect measurements indicated a significant enhancement in electrical properties, with conductivity increasing from 55.56 to 238.10 (Ω·cm)-1 and carrier concentration rising from 1.20 × 1020 to 3.60 × 1020 cm⁻³. The maximum mobility (4.79 cm2.V-1.s-1) is observed at 3% Ce, representing optimal doping. In general, SnO2:Ce (3%) exhibited the best combined structural, optical, and electrical performance, making it a promising candidate for advanced optoelectronic and energy applications.