White-color light emitters from single organic molecule without heavy metals are valuable for practical applications in organic light-emitting devices. In this study, carbazole (Cz)-dibenzofuran (DBF) donor-acceptor dyads are designed for white-color light emitters. Originally, these molecules show photoluminescence (PL) in near ultraviolet region. However, upon successive ultraviolet (UV) irradiation, white-color PL appears, comprising dual-color phosphorescence from the amorphous and crystalline state of the dyad. A continuous UV irradiation makes the twisting angle between the Cz and DBF planes flatten through the triplet-excited state, which proceeds crystallization. Thermal annealing and UV irradiation can switch the blue- and white-color phosphorescences from the dyad. Furthermore, charge injection generates white-color electroluminescence. The materials with PL color modulation ability by UV-light irradiation and heating can be applicable as light- and thermo-sensors.