Organic photovoltaic cells utilizing ultrathin sensitizing layer

A photosensitive device comprising:na first electrode and a second electrode;a series of organic photoactive layers disposed between the first electrode and the second electrode, each layer in the series being in direct contact with a next layer in the series, the series of organic photoactive layers being arranged to form at least one donor-acceptor heterojunction, the series comprising:na first organic photoactive layer comprising a first host material serving as a donor;a second organic photoactive layer comprising a second host material disposed between the first organic photoactive layer and a third organic photoactive layer, the third organic photoactive layer comprising a third host material serving as an acceptor; andthe second organic photoactive layer comprising a plurality of islands of the second host material, the first organic photoactive layer being in direct contact with the third organic photoactive layer in-between the islands, thus forming a first donor-acceptor heterojunction;wherein the first host material, the second host material, and the third host material are different, andwherein the second organic photoactive layer serves as an acceptor relative to the first organic photoactive layer, thus forming a second donor-acceptor heterojunction with the first organic photoactive layer or as a donor relative to the third organic photoactive layer, thus forming a third donor-acceptor heterojunction with the third organic photoactive layer, and a distance from any point within the second host material of the second organic photoactive layer to a boundary of that layer is not more than one exciton diffusion length over a majority of the area of the second organic photoactive layer.