An organic electrophosphorescent white-light-emitting device (see Figure) containing green, red, and blue emitters doped into a 9 nm thick wide-bandgap material is shown to attain a maximum forward viewing power efficiency of (26+/-3) 1m W-1. The high power efficiency is attributed to the efficient confinement of excitons and charge within the emissive layer, a thin emissive layer, and highly efficient blue electrophosphorescent dopant.