Researchers have developed an organic lighting device with “100 percent internal quantum efficiency” by employing newly designed host materials coupled with optimized device architecture. What's particularly significant about the researchers' work is that their optimized device adopts an even simpler structure than any yet reported by other research groups.
“There is no waste of electricity,” Jabbour says. “All the current you are putting into the device is being used to produce light. It's the first time something like this has been demonstrated. Nobody else has shown a 100 percent internal quantum efficiency for lighting devices using a single molecular dopant to emit white light.”
The achievement promises significant progress in the development of solid-state lighting based on OLED technology that can be manufactured at low costs.
Wikipedia discusses the efficiency of lighting and alternatives
Quality halogen incandescents are closer to 9% efficiency.
An incandescent light bulb, with 5% efficiency, is less efficient than fluorescent lamp (7%-15% efficiency)
A table of luminous efficacy is here
An average of 8.8% of electricity used in a home in the USA is for lighting. So replacing all incandescent lights with this lighting would save 8.4% of our electricity usage.