Structure and Properties of Thin Films Prepared on Flexible Substrates from SnCl4-Derived Solutions

Thin transparent films of SnO2 were obtained from aqueous–alcohol solutions of SnCl4 on a flexible polyethylene terephthalate (PET) substrate by spray pyrolysis at 100 °C. The influence of the addition of aqueous ammonia to the film-forming solution on the different properties has been studied. Properties studied include surface morphology, phase composition and transparency of the formed films and the crystallization processes and band gap of the film material. It was found that the addition of aqueous ammonia causes the formation of skeletal crystals (NH4)2[SnCl6] with a perovskite structure in the film structure. The resulting films are promising for use in the technology of manufacturing flexible solar cells.