Mehrab Rahman
Tin dioxide (SnO 2 ) is a versatile, wide-bandgap (≈3.6 eV) n-type semiconductor whose thin-film form has been deployed in transparent electrodes, environmental sensors, energy storage devices, and photocatalysis. Its functional performance in each application hinges on precise control of properties – carrier concentration, crystallinity, defect density, morphology, and surface chemistry – achieved via tailored deposition and doping strategies. This study adopts an application-driven perspective, systematically examining how film engineering (e.g., Deposition Techniques, temperature, atmosphere, film thickness, and substrate type) and compositional tuning (F, Sb, Nb, transition-metal and rare-earth doping, oxygen stoichiometry) modulate key properties. Progress is highlighted in achieving high transparency and conductivity for TCO films (Sb- and F-doped SnO 2 ), enhanced surface reactivity and selectivity for gas sensors, increased charge capacity and stability for battery electrodes, and improved light absorption and charge transport for photocatalytic/photoelectrochemical devices. The review identifies enduring challenges such as the conductivity–transparency trade-off, defect-induced losses, and scale-up reproducibility. Future directions are outlined, including unexplored research, novel co-doping schemes, heterostructure and interface engineering, and data-driven optimization, to guide the targeted design of SnO 2 films. This integrative, application-focused review provides a roadmap for the "property-by-design" of SnO 2 thin films in next-generation materials technologies.