The relevance of this dissertation research is the creation of new radiation-resistant and mechanically stable photosensitive functional materials and device structures of flexible optoelectronics and thermoelectrics using inexpensive and suitable for mass production hydrochemical methods for obtaining nanostructured layers of zinc oxide undoped (ZnO) and doped with indium (ZnO:In) and their composites with biopolymer nanocellulose and silver nanoparticles on the surface of solid and flexible film substrates and fabrics.
The scientific novelty of the obtained results is as follows. Hydrochemical methods have been developed for obtaining nanostructured ZnO and ZnO:In films with high resistance to treatment with glow-discharge hydrogen plasma, irradiation with high doses of an electron beam, and ultraviolet UVC radiation. The stages of the technological process that provide optimal thermoelectric properties of nanostructured ZnO and ZnO:In films on flexible substrates are determined. The influence of treatments with ultraviolet UVC radiation, hydrogen-plasma glow discharge, high doses of electron beam irradiation, and vacuum annealing on point defects and their complexes in the crystal lattice of nanostructured ZnO and ZnO:In films obtained by hydrochemical methods has been studied. The conditions for providing superhydrophobic properties of fabrics with nanostructured ZnO:In films according to the Cassie-Baxter model have been studied, and the effect of ultraviolet radiation on the water-repellent properties of such fabrics has been shown. The influence of VO oxygen vacancies resulting from vacuum annealing in ZnO and ZnO:In nanostructures on the expansion of the zinc oxide photosensitivity spectrum from the ultraviolet to the visible and near-infrared ranges has been determined. The effect of localized surface plasmon resonance and double Schottky barriers at the Ag-ZnO interface on the photosensitivity of flexible device structures of photoconductive photodetectors with respect to ultraviolet, visible, and near-infrared radiation has been studied.
The results obtained are of practical importance. Thus, the dissertation created flexible coatings for protection from solar ultraviolet in terrestrial conditions based on thin nanostructured films of ZnO and ZnO:In, obtained by hydrochemical methods on flexible substrates from cheap polyethylene terephthalate, corresponding to the category "excellent" (50+) according to international standard ISO 2443:2012(E) “Determination of sunscreen UVA photoprotection in vitro”. A durable superhydrophobic textile based on polyester fabric coated with nanostructured ZnO:In layers has been obtained, which does not lose its water-repellent properties after washing and/or exposure to ultraviolet rays of sunlight. Efficient flexible light-sensitive device structures based on nanostructured ZnO and ZnO:In films on polyimide substrates, as well as on the basis of a thin-film nanocomposite with a nanocellulose matrix and ZnO:In filler, have been developed. The latter is promising for use in a new photoresistor design, in which the matrix not only protects the ZnO:In functional semiconductor from mechanical damage and atmospheric influences, but also increases the spectral responsivity, external quantum efficiency, and specific detectivity of the flexible broadband photodetector to the level of the best modern samples. Flexible light-sensitive device structures for highly effic ient photoconductive photodetectors based on nanostructured zinc oxide films obtained by hydrochemical methods on polyimide substrates ZnO/PI and on its nanocomposite with silver nanoparticles ZnO_Ag/PI have been developed. In the latest designs of devices, due to localized surface plasmon resonance and double Schottky barriers at the Ag-ZnO interface, the spectral responsivity, external quantum efficiency, and specific detectivity are increased to the level of the best modern samples of flexible broadband photodetectors. Planar flexible thin-film thermoelectric elements are fabricated based on nanostructured ZnO and ZnO:In layers annealed in vacuum at 300°C on polyimide substrates. The functional device structure of thin-film thermocouples with ZnO/PI n-type TE elements and p-type metal chromel TE elements is obtained. Flexible planar thermoelectric elements are made on the basis of nanostructured ZnO and ZnO:In films on polyimide substrates with thin-film ohmic contacts, the output thermoelectric parameters of which correspond to modern miniature and flexible thermoelectric devices, but have a significant cost advantage.
The practical results of the work are protected by the patent of Ukraine for a utility model No 150983 ("Manufacturing method of flexible textile thermoelectric module" Publ. Bull. No. 20 dated 18.05.2022). The results of the dissertation were introduced into the technological process by the Limited Liability Company "MYRENERHOKOM" (Kharkіv).
