Investigation on the material properties of ZnO nanorods deposited on Ga-doped ZnO seeded glass substrate: Effects of CBD precursor concentration

Abstract

Optimized Ga-doped ZnO (GZO) seed layer was coated onto a glass substrate where ZnO nanorods (ZNRs) were grown via a facile chemical bath deposition (CBD) technique. The concentrations ([Zn (NO3)2]/[C6H12N4]) ratio was maintained at 1, at 90°C for 90 min. Lower thermodynamic barrier was used. This was achieved by growing a GZO NPs seed layer that provided nucleation sites which in turn enhanced the optical properties and the aspect ratios hence ensuring uniform distribution of ZNRs. Investigations of CBD growth concentrations (0.005, 0.03, 0.05, 0.07, and 0.1 M) effects on the material properties of ZNRs were carried out. The as-prepared ZNRs displayed crystalline wurtzite structures. The observed structure had c-axis preference in most of the obtained samples. An increase in size of the crystallites and 002 peak intensity was observed as the growth concentration increased. The SEM micrographs and AFM images showed a direct relation between the length, particle size of the ZNRs, and the precursor concentration. Similarly, the PL spectra showed the excitonic peak intensity increased to a maximum at a precursor concentration of 0.05 M and decayed as the concentration levels increased. Enhancement of the UV and visible light emissions intensity ratios of the ZNRs prepared at lower concentrations was also observed. This is an indication of high optical quality. A higher %T at lower growth concentration and variation of the band gap energy values (3.10–2.30 eV) as the growth concentration is increased were observed from the UV-VIS analysis. The as-prepared ZNRs samples deposited on GZO transparent conducting film were highly luminescent composing of well-aligned ZNRs and perfect crystallization obtained at the 0.05 equimolar precursor concentration of [Zn (NO3)2]/[C6H12N4] solution. The as-grown ZNRs with the observed material properties can be applied in dye-sensitized solar cells production, serving as a photoanode.