US Patent 7888855 Mixed semiconductor nanocrystal compositions

Composition comprising one or more energy donors and one or more energy acceptors, wherein energy is transferred from the energy donor to the energy acceptor and wherein: the energy acceptor is a colloidal nanocrystal having a lower band gap energy than the energy donor; the energy donor and the energy acceptor are separated by a distance of 40 nm or less; wherein the average peak absorption energy of the acceptor is at least 20 meV greater than the average peak emission energy of the energy donor; and wherein the ratio of the number of energy donors to the number of energy acceptors is from about 2:1 to about 1000:1.