Patent questioning fullerene electroluminescence application

The most recent patent to mention fullerenes (as of Nov. 18, 2004) questions, rather than supports, fullerene use in electroluminescent devices:

Although a large amount of research and investigation was conducted on the alternating current electroluminescent devices, the devices never achieved practice application although they were originally highly touted as a room lighting sources. Unfortunately, at high brightness levels the AC electroluminescent devices exhibited a very short life, and after about 1963, most of the research into the AC electro-luminescence devices was severely curtailed.

The most recent efforts in this area have been directed to a molecular carbon (e.g., a form of carbon known as fullerene-60) system. The high voltage drive requirements, the associated high cost of drive circuitry, poor stability and lack of color capability have made these devices cost prohibitive.

[from US 6,819,649]