PHOTOACTIVE MATERIALS CONTAINING BULK AND QUANTUM-CONFINED SEMICONDUCTOR STRUCTURES AND OPTOELECTRONIC DEVICES MADE THEREFROM
The present invention provides photoactive materials that include quantum-confined semiconductor nanostructures in combination with non-quantum confined and bulk semiconductor structures to enhance or create a type II band offset structure. The photoactive materials are well-suited for use as the photoactive layer in photoactive devices, including photovoltaic devices, photoconductors and photodetectors.
1 . A photoactive material comprising a plurality of quantum-confined semiconductor nanostructures and a plurality of non-quantum-confined semiconductor structures, wherein the plurality of quantum-confined semiconductor nanostructures and the plurality of non-quantum confined semiconductor structures have a type II band offset.
2 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures are made from a semiconductor material and further wherein the semiconductor material exhibits a type II band offset with respect to the plurality of non-quantum-confined semiconductor structures as a quantum-confined material, but exhibits a type I band offset with respect to the plurality of non-quantum-confined semiconductor structures as a bulk material.
3 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures and the plurality of non-quantum-confined semiconductor structures comprise Group IV semiconductors.
4 . The photoactive material of claim 3 , wherein the plurality of quantum-confined semiconductor nanostructures are germanium nanostructures, and the plurality of non-quantum-confined semiconductor structures comprise one of amorphous silicon, single-crystalline silicon, and polycrystalline silicon.
5 . The photoactive material of claim 4 , wherein the germanium nanostructures have dimensions of no more than about 35 nm, and the plurality of non-quantum-confined semiconductor structures have at least one dimension no greater than 10 nm.
6 . The photoactive material of claim 3 , wherein the plurality of quantum-confined semiconductor nanostructures are tin nanostructures, and the plurality of non-quantum-confined semiconductor structures comprise one of amorphous silicon, single-crystalline silicon, polycrystalline silicon, amorphous germanium, single-crystalline germanium, and polycrystalline germanium.
7 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures are silicon nanocrystals and the plurality of non-quantum-confined semiconductor structures are amorphous silicon.
8 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures and the plurality of non-quantum-confined semiconductor structures are amorphous structures.
9 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures and the plurality of non-quantum-confined semiconductor structures are contained in a single layer.
10 . The photoactive material of claim 1 , wherein the at least one of the plurality of quantum-confined nanostructures and the plurality of non-quantum-confined semiconductor structures include at least two elements selected from the group consisting of Si, Ge, and Sn.
11 . The photoactive material of claim 1 , wherein the photoactive material comprises a first sublayer and a second sublayer adjacent to the first sublayer, wherein the first sublayer includes the plurality of quantum-confined semiconductor nanostructures, and the second sublayer includes the plurality of non-quantum-confined semiconductor structures.
12 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures are single crystalline silicon nanoparticles having dimensions of no greater than about 10 nm, and the plurality of non-quantum-confined semiconductor structures are amorphous silicon nanoparticles.
13 . The photoactive material of claim 1 , wherein the plurality of quantum-confined semiconductor nanostructures are single crystalline silicon nanoparticles having dimensions of no greater than about 10 nm, and the plurality of non-quantum-confined semiconductor structures are amorphous germanium nanoparticles.
14 . An optoelectronic device comprising:
(a) a first electrode;
(b) a second electrode; and
(c) a photoactive layer, the photoactive layer comprising a plurality of quantum-confined semiconductor nanostructures and a plurality of non-quantum-confined semiconductor structures having a type II band offset in electrical communication with the first electrode and the second electrode.
15 . A photoactive material comprising a first sublayer and a second sublayer adjacent to the first sublayer, wherein the first sublayer includes a plurality of quantum-confined semiconductor nanostructures, and the second sublayer includes a bulk semiconductor, wherein the plurality of quantum-confined nanostructures and the bulk semiconductor have a type II band offset.
16 . The photoactive material of claim 15 , wherein the plurality of quantum-confined semiconductor nanostructures are made from a semiconductor material characterized in that, as a quantum-confined material it exhibits a type II band offset with respect to the bulk semiconductor, but as a bulk material it exhibits a type I band offset with respect to the bulk semiconductor.
17 . The photoactive material of claim 15 , wherein the plurality of quantum-confined semiconductor nanostructures and the bulk semiconductor comprise Group IV semiconductors.
18 . The photoactive material of claim 17 , wherein the quantum-confined semiconductor nanostructures are germanium nanostructures, and the bulk semiconductor comprises one of amorphous silicon, single-crystalline silicon, and polycrystalline silicon.
19 . The photoactive material of claim 17 , wherein the plurality of quantum-confined semiconductor nanostructures are tin nanostructures, and the bulk semiconductor comprises one of amorphous silicon, single-crystalline silicon, polycrystalline silicon, amorphous germanium, single-crystalline germanium, and polycrystalline germanium.
20 . The photoactive material of claim 15 , wherein the plurality of quantum-confined semiconductor nanostructures and the bulk semiconductor are made from the same semiconductor material.
21 . The photoactive material of claim 20 , wherein the plurality of quantum-confined semiconductor nanostructures are silicon nanocrystals and the bulk semiconductor comprises amorphous silicon.
22 . The photoactive material of claim 15 , wherein the plurality of quantum-confined nanostructures include at least two elements selected from the group consisting of Si, Ge and Sn.
23 . A photoactive material comprising a plurality of quantum-confined semiconductor nanostructures embedded in a layer of bulk semiconductor, wherein the plurality of quantum-confined semiconductor nanostructures and the layer of bulk semiconductor have a type II band offset.
24 . The photoactive material of claim 23 , wherein the plurality of quantum-confined semiconductor nanostructures are made from a semiconductor material, and further wherein the semiconductor material exhibits a type II band offset with respect to the bulk semiconductor as a quantum-confined material, but exhibits a type I band offset with respect to the bulk semiconductor as a bulk material.