Organic molecules of DIDB can inherently assemble into fluorescent green-emissive microwires with a low photoluminescence quantum efficiency (PLQY) of 1.0%. Impressively, by doping DIDB into the nonluminous 4-iodobenzonitrile crystal matrix with a molar ratio of 1 : 100, phosphorescent yellow-emissive microwires with a much higher PLQY of 50.5% are obtained.