Accelerated growth of nanostructured ZnO films via low temperature microwave-assisted H2O oxidation for solar cell applications

Accelerated formation of novel nanostructured ZnO films via microwave-assisted H2O oxidation. [Display omitted] •Novel nanostructured ZnO films were designed via microwave-assisted H2O oxidation.•The formation of ZnO films was dramatically accelerated under microwave irradiation.•Microwave-asssisted H2O oxidation is a promising route to obtain high-quality ZnO. Herein, the accelerated growth of nanostructured ZnO films via a facile, sustainable and low-temperature microwave-assisted H2O oxidation is presented for the first time. This novel technique involves the oxidation of Zn thin films in pure H2O under microwave irradiation to form nanostructured ZnO films. ZnO nanorods (NRs) were readily obtained after 30 min of microwave irradiation without the presence of any catalysts, surfactant or ligands. Moreover, increasing the irradiation time led to the conversion of NRs to honeycomb-like structures composed of nanotubes (NTs). The high-quality crystalline nature of the nanostructured ZnO films was established from XRD, Raman and HRTEM analyses. Based on XPS analysis, the duration of irradiation time controlled the amount of OH– group on the surface of the ZnO films. Insignificant amount of oxygen vacancies and OH– group were found for the films obtained at longer irradiation time. Most notably, the ZnO film with honeycomb-like structure formed after 2 h of irradiation exhibited the most promising electron-transporting capability based on steady-state PL analysis. These results highlight the potential of H2O-oxidized nanostructured ZnO films as electrode for photovoltaic devices. Finally, this study offers a promising approach which could sustain the requirements of future ZnO-based optoelectronic devices.