Patent ID: 8395042

Claim:
A photovoltaic device comprising: (a) a first conductor layer; (b) a second conductor layer; (c) an active layer, wherein said active layer is situated between said first and said second conductor layers, wherein said active layer comprises a matrix material and a plurality of quantum dots deposited in said matrix material, wherein each of said quantum dots has a bandgap, wherein the position of each of said quantum dots in said active layer is based on the size of its bandgap, wherein said quantum dots with larger bandgaps are positioned closer to said first conductor layer than said quantum dots with smaller bandgaps, whereby a bandgap gradient is present in said active layer; wherein the matrix material comprises an insulator; wherein adjacent quantum dots are separated by distances in a direction of the bandgap gradient that allow charge tunneling between the adjacent quantum dots; and wherein adjacent quantum dots are also separated from each other in directions perpendicular to the direction of the bandgap gradient.