We demonstrate efficient organic white light-emitting devices (LEDs), using N,N8-diphenyl-N,N8-bis(1-naphthyl)-(1,18-biphenyl)-4,48-diamine (NPB) as the hole-transporting layer, 1,6-bis(2-hydroxyphenyl)pyridine boron complex [(dppy)BF)] as the emitting layer, tris-(8-hydroxyquinoline)aluminum (Alq) as the electron-transporting and chromaticity-tuning layer. The white light comes from exciplex emission at the solid-state interface between (dppy)BF and NPB in addition to the exciton emission from NPB and (dppy)BF, respectively. The chromaticity of white emission can be tuned by adjusting the thickness of the Alq layer. The white LEDs with an Alq thickness of 15nm exhibit a maximum luminescence of 2000cd/m2 and efficiency of 0.58lm/W, and the Commission Internationale De l'Eclairage coordinates of resulting emission vary from (0.29,0.33) to (0.31,0.35) with increasing forward bias from 10 to 25V. The region is very close to the equienergy white point (0.33,0.33).