APPARATUS AND METHODS OF MIXING AND DEPOSITING THIN FILM PHOTOVOLTAIC COMPOSITIONS
Improved methods and apparatus for forming thin-film layers of semiconductor material absorber layers on a substrate web. According to the present teachings, a semiconductor layer may be formed in a multi-zone process whereby various layers are deposited sequentially onto a moving substrate web. At least one layer is deposited from a mixed gallium indium source.
1 . A vapor deposition apparatus for use in manufacturing thin-film photovoltaic semiconductors, comprising:
a roll-to-roll assembly configured to transport a flexible substrate through plural zones along a processing path;
at least one zone having a substantially enclosed gallium and indium deposition assembly configured to deposit a layer comprised of gallium and indium in the presence of selenium gas onto the substrate; and
a crucible containing pre-mixed gallium and indium in a predetermined ratio;
wherein the gallium and indium deposition assembly is configured to deposit gallium and indium evaporated from the crucible.
2 . The apparatus of claim 1 , further comprising:
a monitoring station configured to monitor amounts of gallium and indium deposited on the substrate.
3 . The apparatus of claim 2 , wherein the monitoring station includes:
at least one sensor configured to allow measurement of a ratio of gallium and indium; and
at least one processor configured to determine appropriate adjustment of gallium and indium deposition.
4 . The apparatus of claim 3 , further comprising:
a controller configured to adjust the temperature of the crucible.
5 . The apparatus of claim 2 , wherein the monitoring station includes:
at least one sensor configured to allow measurement of the thickness of gallium and indium deposited on the substrate; and
at least one processor configured to determine appropriate adjustment of gallium and indium deposition.
6 . The apparatus of claim 5 , further comprising:
a controller configured to adjust the temperature of the crucible.
7 . An apparatus for depositing a mixture of gallium and indium onto a flexible substrate, comprising:
a first crucible containing pre-mixed gallium and indium and a heating element in thermal communication with the crucible;
a vapor manifold connected to the crucible such that vapor may pass from the crucible to the manifold; and
a nozzle connected to the manifold through which a heated mixed gallium and indium vapor exits the source.
8 . The apparatus of claim 7 , wherein the heating element is disposed in an upper portion of the apparatus.
9 . The apparatus of claim 7 , wherein the nozzle is formed at least in part by the heating element.
10 . The apparatus of claim 7 , further comprising a second crucible containing a material selected from the set consisting of gallium and indium, and wherein the first and second crucibles are collectively configured to deposit gallium and indium onto the substrate with a gallium to gallium indium ratio in the range of 25%-35% at a top surface of the deposited layers.
11 . The apparatus of claim 10 , wherein the first and second crucibles are collectively configured to deposit gallium and indium onto the substrate with a gallium to gallium indium ratio in the range of 25%-35% in a region extending between a depth of 0.6 μm below the top surface and a depth of 1.0 μm below the top surface.
12 . A vapor deposition apparatus for use in manufacturing thin-film photovoltaic semiconductors, comprising:
a roll-to-roll assembly configured to transport a flexible substrate through plural zones along a processing path;
a first gallium and indium deposition assembly configured to deposit a first layer including gallium and indium onto the substrate by evaporating pre-mixed gallium and indium from a first crucible in a first predetermined gallium to gallium indium ratio; and
a second gallium and indium deposition assembly configured to deposit a second layer including gallium and indium onto the first layer by evaporating pre-mixed gallium and indium from a second crucible in a second predetermined gallium to gallium indium ratio.
13 . The apparatus of claim 12 , wherein the first gallium to gallium indium ratio is smaller than the second gallium to gallium indium ratio.
14 . The apparatus of claim 12 , wherein the second gallium to gallium indium ratio is in the range of 10% to 45%.
15 . The apparatus of claim 12 , wherein the second gallium to gallium indium ratio is in the range of 25% to 35%.
16 . The apparatus of claim 12 , wherein the first and second gallium and indium deposition assemblies are collectively configured to produce a gallium to gallium indium ratio in the range of 25%-35% at a top surface of the deposited layers.
17 . The apparatus of claim 16 , wherein the first and second gallium and indium deposition assemblies are collectively configured to produce a local minimum gallium to gallium indium ratio in the range of 20%-30% at depths between 0.4 μm and 0.5 μm below the top surface.
18 . The apparatus of claim 17 , wherein the first and second gallium and indium deposition assemblies are collectively configured to produce a maximum gallium to gallium indium ratio of between 0.4 and 0.5.
19 . The apparatus of claim 18 , wherein the first and second gallium and indium deposition assemblies are collectively configured to produce a gallium to gallium indium ratio that declines slightly between the top surface and a depth of 0.1 μm below the top surface.
20 . The apparatus of claim 12 , wherein the first and second gallium and indium deposition assemblies are collectively configured to produce a gallium to gallium indium ratio in the range of 25%-35% in a region extending between a depth of 0.6 μm below a top surface of the deposited layers and a depth of 1.0 μm below the top surface.