We demonstrate a promising single layer white light-emitting device using a dimeric trimeric phenylenvinylene derivative as emitting layer. The broad electroluminescence emission band is composed of blue component from singlet excited state of individual 2, 5, 2′, 5′-tetra (p-trifluoromethylstyryl)-biphenyl molecule and long-wavelength electromer emission in electroluminescence. Therefore, white-light emission can also be obtained with a typical three-layer structure of ITO/NPB (50 nm)/TFM-TSB (50 nm)/Alq3 (30 nm)/LiF/Al device. The maximum brightness of this device is 809 cd/m2 at 217 mA/cm2 and 13 V, and the maximum luminous efficiency is 1.49 cd/A at 11 mA/cm2 and 8 V.