Multimorphological zinc oxide: Synthesis and investigation of solar driven hydrogen generation and optoelectrical properties

This dissertation is based on a highly distinctive, diosyncratic, and multiversant metal oxide semiconductor, zinc oxide (ZnO). More specifically, the work comprises the utilization of ZnO as both a highly efficient photoanode material and a photoluminescent thin film that serves both energy-based and optoelectronic applications. The emphasis within the scope of the dissertation is made on the morphological diversity of ZnO and the ways to utilize this as an advantage in photoelectrochemical and light-emitting appliances. Essentially, the dissertation consists of three main parts details of which are elaborated as follows; (i) In the first part, ZnO thin films are grown via hydrothermal routes in three diverse morphologies on flexible stainless steel substrates. Here, the aim was to examine the potential of implementation of ZnO-based photoelectrodes into strained, curvature systems by analyzing their photon-to-current conversion efficiencies under flexed conditions. The obtained performances have been correlated with detailed material characterizations offering an integrated vision of the system's operability. (ii) In this part, ZnO thin films were targeted to be grown on specific patterns without engaging costly and time-consuming lithographic techniques. By developing a smart approach, selective growth of ZnO has been attained by taking advantage of its seeding-layer selective nature. To put it differently, knowing that ZnO nanostructures have nucleation and growth pathways that vary strongly depending on the seeding layer, a dual ZnO/Ti stack film has been introduced onto the system. At this stage, Ti was the growth prohibiting agent, while ZnO seeding layer beneath played the role of growth provider. Through the careful utilization of a nanosecond fiber laser system, Ti layers have been successfully removed from the predetermined regions, consequently providing the selective allocation of ZnO nanostructures. By altering the ablation power, a concurrent growth of two different structures has been provided within the same hydrothermal solution and on the same substrate. This nanostructure duality has severely boosted the photoluminescence (PL) ability of ZnO films outscoring the light-emitting performances of individual nanostructures. (iii) In the final part of the dissertation, dual ZnO nanostructured films have been deposited with 0D and 3D inorganic halide perovskite (IHP) layers to maximize the PL performances and prolong the minority carrier lifetimes for future light-emitting device applications. With the incorporation of IHP layers a substantial improvement in emission, especially within the visible range, has been observed. Moreover, the increased carrier lifetimes have shown the promising characteristics of patterned and IHP sensitized multi-morphological ZnO films.