Solid state metathesis synthesis for ZnO-based materials towards applications in light-emitting diodes and ultra-violet-sensing devices

Abstract

Solid state metathesis (SSM) has gained much attention for the synthesis of ZnObased semiconductors. SSM is a synthesis method that avoids organic solvents, high temperature calcination, and it is simple and fast. Co-doped ZnO has already been synthesized by several other methods (co-precipitation method, sol-gel). We wanted to use SSM to make Co-doped ZnO, in which Zn²⁺ ions are replaced by Co²⁺ ions. The thesis work goal was to prepare Co-doped ZnO to use it in light emitting diodes as a red light emitter. Raman spectra of the attempted Co-doped ZnO confirms the formation Co(OH)₂ as a secondary phase, which in turns converts into Co₃O₄ during high temperature calcination. There were no characteristic peaks in the visible region of UV-Vis spectra that would correspond to the emission of red light. Stoichiometric ZnO films are good candidates for use in various sensing devices. The frequency-dependent UV response of SSM-produced ZnO films were studied under AC conditions. After storing in the dark for several days, the UV responses were studied by electrochemical impedance spectroscopy (EIS). The resulting data allow determination, for each individual film, what range of frequencies are appropriate for use in UV sensing.