Passivating window and capping layer for photoelectrochemical cells
An aspect of the present disclosure is a photoelectrochemical device that includes a first cell that includes a first semiconductor alloy, a capping layer that includes a second semiconductor alloy, and a passivating layer that includes a third semiconductor alloy, where the passivating layer is positioned between the first cell and the capping layer, and at least a portion of the capping layer is configured to be in direct contact with an electrolyte.
1. A photoelectrochemical device comprising:
a first cell comprising an n-layer and a p-layer;
a second cell comprising GaInAs;
a capping layer comprising a first alloy of n-type Ga x In (1-x) P; and
a passivating layer comprising a second alloy of Al u In (1-u) P, wherein:
0<×<1 and 0<u<1,
both the n-layer and the p-layer comprise AlGaAs,
the n-layer is positioned between the p-layer and the passivating layer,
the first cell is positioned between the second cell and the passivating layer,
the passivating layer is positioned between the first cell and the capping layer,
the capping layer has a thickness between 10 nm and 20 nm, inclusively, and
at least a portion of the capping layer is configured to withstand direct contact with an electrolyte.
2. The photoelectrochemical device of claim 1 , wherein x is about 0.51.
3. The photoelectrochemical device of claim 1 , wherein the first alloy further comprises at least one of selenium, tellurium, sulfur, or silicon.
4. The photoelectrochemical device of claim 1 , wherein u is about 0.53.
5. The photoelectrochemical device of claim 1 , wherein the second alloy further comprises at least one of selenium, tellurium, sulfur, or silicon.
6. A method for producing a photoelectrochemical device, the method comprising:
growing by an epitaxial method a first cell comprising an n-layer and a p-layer on a substrate;
growing by an epitaxial method a second cell comprising GaInAs on the first cell;
attaching the second cell to a handle;
removing the substrate from the first cell, resulting in the exposing of a surface of the first cell;
depositing a passivating layer comprising a first alloy of Al u In (1-u) P on the surface; and
depositing a capping layer comprising a second alloy of n-type Ga x In (1-x) P on the passivating layer, wherein:
0<×<1 and 0<u<1,
both the n-layer and the p-layer comprise AlGaAs,
the n-layer is positioned between the p-layer and the passivating layer,
the capping layer has a thickness between 10 nm and 20 nm, inclusively, and
at least a portion of the capping layer is configured to be in direct contact with an electrolyte.
7. The photoelectrochemical device of claim 1 , wherein the passivating layer has a thickness between 10 nm and 20 nm, inclusively.
8. The photoelectrochemical device of claim 1 , further comprising: a back reflector comprising at least one of gold or silver, wherein: the second cell is positioned between the back reflector and the first cell.
9. The photoelectrochemical device of claim 1 , wherein:
the second cell further comprises an n-layer and a p-layer,
both the n-layer and the p-layer of the second cell comprise GaInAs, and
the n-layer of the second cell is positioned between the p-layer of the second cell and the first cell.
10. The photoelectrochemical device of claim 1 , wherein both the n-layer and the p-layer of the first cell comprise about Al 0.23 Ga 0.77 As.
11. The photoelectrochemical device of claim 9 , wherein both the n-layer and the p-layer of the second cell comprise about Ga 0.89 In 0.11 As.