PXRD was then carried out to gain the relationship between PL change and molecular packing. As indicated in Fig. , the PXRD patterns of DCzPy displayed numerous sharp diffraction peaks in the pristine powders, suggestive of their good crystallinity with well-ordered molecular packing. Upon gently grinding, some diffraction peaks of DCzPy disappeared in PXRD patterns, but many intense diffraction peaks were still observed, suggesting that their crystalline packing modes have given rise to some changes. Further increasing the grinding force, the ground powders also exhibited distinct peaks and indicated a partially crystalline state. It is inferred that the long-range ordered structures of DCzPy crystals were destroyed after grinding to afford many small crystalline fragments. Analysis from PXRD revealed that MC behaviors of DCzPy are attributed to the solidstate crystal-to-crystal morphology transition.