Red shift of green-emission band has been observed for fac tris(2-phenylpyridine) iridium (Ir(ppy)3) doped in polycarbonate at 8 K during time evolution after 355-nm laser of 1-ns pulse width. We explain the peak shift and vibronic structure of the emission band using the Franck-Condon principle and the model of (1) three zero-field splitting substates of the triplet state, (2) relaxation processes among the three substates, and (3) different Huang-Rhys factors for these substates. Good agreement was obtained between the calculated and measured emission spectra at various delay times.