The quest for more efficient conversion of electricity (Watt) into light (Lumens) has produced amazing results in the last decade. The Edison bulb lamp that dominated for a hundred years is not being decommissioned. It could deliver 10-17 Lumens per Watt. Bulb lamps used in public illumination, based on high pressure sodium vapour could reach 140 Lumens per Watt (between 40 and 140...) but they are bulky and expensive. Halogen lamps double the efficiency of a incandescent bulb lamp.
In the last ten years LED based lamps can get 100 Lumens per Watt and the very best LED based lamp earlier this year broke the 300 lumen per Watt barrier.
Now researchers at Tohoku University in Japan have shown a process to use CNT (Carbon NanoTubes) as a source of light. They have found that a solution of CNT can be sprayed on the surface of a cathode using surfactant that results in an ordered structure that when subject to an electric field causes electrons to move in the CNT (they have quasi zero resistance, hence highly efficient) and hit a phosphorous layer creating light emission.
The prototype has an efficiency of 60 Lumens per Watt which, although it is lower than what has been achieved with LED is quite promising. Remember that present efficiency of LED is the result of a decade of progress whilst here we are at a prototype stage of a technology.
Another application of CNT that might become a normal presence in our home landscape in the next decade.