We fabricated a single-layer white light electroluminescent (EL) device consisted of emitting layer contains molecularly doped poly(N-vinylcabazole) (PVK) with 30 wt% of 2,5-bis(5-tert-bytyl-2-benzoxazolyl)thiophen (BBOT), 2.17 mol% of N,N'-diphenyl-N,N'-bis(3-metylphenyl)-1, 1'-biphenyl-4,4'-diamine (TPD) and 0.039 mol% of poly(3-hexylthiophene) (P3HT). In the photoluminescence (PL) spectra, we observed the exciplex formed between PVK and BBOT, TPD and BBOT, respectively. Sequential energy transfer occurred in a mixed emitting layer. Consequently, we achieved white light emission corresponds to Commission Internationale de L'Eclairage (CIE) coordinate of x = 0.295, y = 0.32.