In this study, blue organic light-emitting diodes (OLEDs) using polymer-dopant systems as a light-emitting layer were fabricated. The light-emitting layer was produced via a spin-coating process. The materials used in the light-emitting layer included: poly(9-vinylcarbazole) (PVK) as a matrix material, and blue-emission 4,4′-bis(2,2-diphenylvinyl)biphenyl (DPVBi) as a light-emitting material. The blue OLED was fabricated by blending PVK and DPVBi according to the proportion of mass as specified for a light-emitting layer. Process relevant photophysical mechanisms and energy transfer phenomena were studied using absorption, photoluminescence (PL), photoluminescent excitation, and electroluminescence (EL) spectra. We have learned that there was energy transfer phenomenon between PVK and DPVBi. More specifically, the EL spectrum of PVK:DPVBi was significantly different from the PL spectra of PVK, DPVBi, and PVK:DPVBi, shining to a longer wavelength and showing multiple boarding emission peaks (maximum emission at 465 and 486 nm). The electro-optical characteristics of the blue OLED and the possible origin of the difference between the EL and PL spectra were discussed.