Reply to comment on 'aggregation-induced phosphorescent emission (AIPE) of iridium(III) complexes': origin of the enhanced phosphorescence.

An obvious enhanced phosphorescence emission in the solid state (EPESS) was observed for two iridium(III) complexes with restricted (even fixed) intramolecular rotational motion, which is contrary to the opinion ("restricted intramolecular rotational motion as the origin of EPESS") of Park et al., and our observation confirmed that the pi-pi stacking of adjacent pyridyl rings of ppy ligands played a key role in EPESS.