Disorder driven optical processes in nanocrystalline ZnO

► Optical properties in mechanically milled ZnO powder have been reported. ► Optical absorption estimates that above ∼65 nm red shift is negligible. ► Band tail parameter increases significantly at low grain size regime. ► PL intensity ratio varies exponentially with band tail parameter. ► Overall results indicate that Vo-VZn divacancy related defects are generated.