Photoluminescence spectroscopy of bulk zinc oxide under different annealing conditions was examined. The effect of the annealing atmosphere, temperature and time on the optical properties of zinc oxide were studied to investigate the influence on the intrinsic defects present. The wafers used were bulk +c ZnO grown by Tokyo Denpa using the hydrothermal technique. The annealing effect on both zinc and oxygen faces was investigated. The dominant donor bound exciton related to aluminum, labelled in the literature as I₆ demonstrated a splitting of 0.3 meV. The origin of this splitting has been linked to an interaction between aluminum and hydrogen, through its reaction to atmospheric dependent annealing. The removal of the hydrothermal hydrogen peak at 3.3624 eV has uncovered some fine structure. After Arrhenius analysis of this fine structure it was shown it is excited states of bound excitons. This fine structure has been loosely associated with vibrational and rotational excited states. The behaviour of all the optical features present in the photoluminescent spectra under annealing has a relation with the carrier concentration of the samples.