A rod-coil block copolymer consisting of poly(3-hexylthiophene) (P3HT) and poly(N-vinylcarbazole) (PVK) (P3HT-b-PVK) in a single molecular architecture is prepared as the first example for WOLEDs. By obtaining the phase separated domains in thin film of the resulting block copolymer, it is possible to suppress energy transfer from PVK as wide bandgap units to P3HT as low bandgap blocks, yielding dual emissions for white electroluminescence with CIE coordination of (0.34, 0.33).