Formation of Ohmic back contact for Ag
Techniques for forming an ohmic back contact for Ag 2 ZnSn(S,Se) 4 photovoltaic devices. In one aspect, a method for forming a photovoltaic device includes the steps of: depositing a refractory electrode material onto a substrate; depositing a contact material onto the refractory electrode material, wherein the contact material includes a transition metal oxide; forming an absorber layer on the contact material, wherein the absorber layer includes Ag, Zn, Sn, and at least one of S and Se; annealing the absorber layer; forming a buffer layer on the absorber layer; and forming a top electrode on the buffer layer. The refractory electrode material may be Mo, W, Pt, Ti, TiN, FTO, and combinations thereof. The transition metal oxide may be TiO 2 , ZnO, SnO, ZnSnO, Ga 2 O 3 , and combinations thereof. A photovoltaic device is also provided.
1. A method for forming a photovoltaic device, the method comprising the steps of:
depositing a refractory electrode material onto a substrate;
depositing a contact material onto the refractory electrode material, wherein the contact material comprises a transition metal oxide with a work function below about 4.5 electronvolts (eV), and wherein the contact material as deposited is in direct physical contact with the refractory electrode material;
forming an absorber layer directly on the contact material, wherein the absorber layer comprises silver (Ag), zinc (Zn), tin (Sn), and at least one of sulfur (S) and selenium (Se);
annealing the absorber layer;
forming a buffer layer on the absorber layer; and
forming a top electrode on the buffer layer.
2. The method of claim 1 , wherein the substrate comprises a glass, a ceramic, a metal foil, or a plastic substrate.
3. The method of claim 1 , wherein the refractory electrode material is selected from the group consisting of: molybdenum (Mo), tungsten (W), platinum (Pt), titanium (Ti), titanium nitride (TiN), fluorinated tin oxide (FTO), and combinations thereof.
4. The method of claim 1 , wherein the refractory electrode material has a thickness of from about 0.5 micrometer to about 2 micrometers, and ranges therebetween.
5. The method of claim 1 , wherein the transition metal oxide is selected from the group consisting of: titanium oxide (TiO 2 ), zinc oxide (ZnO), tin oxide (SnO), zinc tin oxide (ZnSnO), gallium oxide (Ga 2 O 3 ), and combinations thereof.
6. The method of claim 1 , wherein the transition metal oxide comprises TiO 2 .
7. The method of claim 1 , wherein the contact material has a thickness of from about 5 nanometers to about 100 nanometers, and ranges therebetween.
8. The method of claim 1 , wherein the absorber layer is annealed at a temperature of from about 400° C. to about 550° C., and ranges therebetween, for a duration of from about 20 seconds to about 10 minutes, and ranges therebetween.
9. The method of claim 1 , wherein the buffer layer comprises a buffer material selected from the group consisting of: copper(I) oxide (Cu 2 O), nickel(II) oxide (NiO), zinc telluride (ZnTe), aluminum phosphide (AlP), molybdenum trioxide (MoO 3 ), cadmium telluride (CdTe), copper(I) iodide (CuI), molybdenum(IV) oxide (MoO 2 ), molybdenum disulfide (MoS 2 ), molybdenum diselenide (MoSe 2 ), and combinations thereof.
10. The method of claim 1 , wherein the buffer layer comprises MoO 3 .
11. The method of claim 1 , wherein the top electrode comprises a transparent conductive oxide.
12. The method of claim 11 , wherein the transparent conductive oxide is selected from the group consisting of: indium-tin-oxide, aluminum-doped zinc oxide, and combinations thereof.
13. The method of claim 11 , further comprising the step of:
forming metal contacts on the top electrode.
14. The method of claim 13 , wherein the metal contacts comprise a metal selected from the group consisting of: gold (Au), silver (Ag), aluminum (Al), nickel (Ni), and combinations thereof.
15. The method of claim 1 , wherein the transition metal oxide is selected from the group consisting of: TiO 2 , SnO, ZnSnO, Ga 2 O 3 , and combinations thereof.