PHOTOVOLTAIC DEVICE AND METHOD OF MANUFACTURING PHOTOVOLTAIC DEVICES
A photovoltaic device includes a supporting layer, a semiconductor layer stack, and a conductive and light transmissive layer. The supporting layer is proximate to a bottom surface of the device. The semiconductor layer stack includes first and second semiconductor sub-layers, with the second sub-layer having a crystalline fraction of at least approximately 85%. A conductive and light transmissive layer between the supporting layer and the semiconductor layer stack, where an Ohmic contact exists between the first semiconductor sub-layer and the conductive and light transmissive layer.
1 . A method for manufacturing a photovoltaic device, the method comprising:
providing a supporting layer proximate to a bottom surface of the device;
depositing a conductive and light transmissive layer above the supporting layer;
depositing a semiconductor layer stack in an amorphous state above the conductive and light transmissive layer, the semiconductor layer stack comprising first and second sub-layers; and
increasing a level of crystallinity in the second sub-layer, the second sub-layer having a crystalline fraction of at least approximately 85% after increasing the level of crystallinity.
2 . The method of claim 1 , wherein the semiconductor layer stack comprises a third sub-layer, the second sub-layer disposed between the first and third sub-layers, the first and third sub-layers each doped with different types of dopants.
3 . The method of claim 2 , wherein a first dopant junction exists between the first and second sub-layers and a second dopant junction exists between the second and third sub-layers, and a junction diffusion width of each of the first and second dopant junctions is 100 nanometers or less after increasing the level of crystallinity in the second sub-layer.
4 . The method of claim 2 , wherein a dopant junction exists between the first and second sub-layers, the dopant junction having a junction diffusion width that does not increase by more than approximately 50 nanometers during increasing the crystallinity of the second sub-layer.
5 . The method of claim 1 , wherein increasing the level of crystallinity occurs after depositing the conductive and light transmissive layer.
6 . The method of claim 1 , wherein the supporting layer has a softening point below 750 degrees Celsius.
7 . The method of claim 1 , wherein the semiconductor layer stack remains in a solid state during increasing the level of crystallinity in the second sub-layer.
8 . The method of claim 1 , wherein increasing the level of crystallinity comprises exposing the second sub-layer to one or more electron beams or one or more continuous-wave laser beams.
9 . A method for manufacturing a photovoltaic device, the method comprising:
providing a substrate;
depositing a reflective electrode above the substrate;
depositing an optical spacer layer above the reflective electrode, the optical spacer layer comprising a conductive and light transmissive material;
depositing a semiconductor layer stack above the optical spacer layer, the semiconductor layer stack deposited in an amorphous state, the semiconductor layer stack comprising first and second sub-layers;
increasing a level of crystallinity in the second sub-layer, the second sub-layer having a crystalline fraction of at least 85% after increasing the level of crystallinity; and
depositing a light transmissive electrode above the semiconductor layer stack.
10 . The method of claim 9 , wherein the semiconductor layer stack remains in a solid state during increasing the level of crystallinity in the second sub-layer.
11 . The method of claim 9 , wherein increasing the level of crystallinity comprises exposing the second sub-layer to one or more electron beams.
12 . The method of claim 9 , wherein increasing the level of crystallinity comprises heating the second sub-layer at a rate of at least approximately 400 degrees Celsius per second.
13 . The method of claim 9 , wherein increasing the level of crystallinity comprises exposing the second sub-layer to one or more continuous-wave laser beams.
14 . A method for manufacturing a photovoltaic device, the method comprising:
providing a light transmissive superstrate;
depositing a light transmissive electrode above the superstrate;
depositing a semiconductor layer stack above the light transmissive electrode, the semiconductor layer stack deposited in an amorphous state, the semiconductor layer stack comprising first and second sub-layers;
increasing a level of crystallinity in the second sub-layer, the second sub-layer having a crystalline fraction of at least 85% after increasing the level of crystallinity;
depositing an optical spacer layer above the semiconductor layer stack, the optical spacer layer comprising a conductive and light transmissive material; and
depositing a reflective electrode above the optical spacer layer.
15 . The method of claim 14 , wherein an Ohmic contact exists between the semiconductor layer stack and the optical spacer layer.
16 . The method of claim 14 , wherein increasing the level of crystallinity occurs after depositing the light transmissive electrode.
17 . The method of claim 14 , wherein the superstrate has a softening point below 750 degrees Celsius.
18 . The method of claim 14 , wherein increasing the level of crystallinity comprises exposing the second sub-layer to one or more electron beams.
19 . The method of claim 14 , wherein increasing the level of crystallinity comprises heating the second sub-layer at a rate of at least approximately 400 degrees Celsius per second.
20 . The method of claim 14 , wherein increasing the level of crystallinity comprises exposing the second sub-layer to one or more continuous-wave laser beams.