The non-catalyzed cycloaddition of eight structurally different azides with cyclooctyne generated in situ by the photolysis of cycloocta-1,2,3-selenadiazole gives 1,2,3-triazole derivatives as the main products. The application of this reaction was demonstrated by the photoconjugation reaction of cycloocta-1,2,3-selenadiazole with an avidin-modified biotin complex to introduce a new strategy in the non-catalyzed synthesis of bioconjugates.