Organic monolayer passivation and silicon heterojunction photovoltaic devices using the same

1. A method for inorganic passivation in a photovoltaic device, the method comprising:

etching a native oxide over an inorganic substrate, the inorganic substrate having a surface;

forming an organic monolayer directly on the surface of the inorganic substrate to form a heterojunction, the organic monolayer having the following formula:

˜X—Y,

wherein X is an oxygen or a sulfur; Y is an alkyl chain, an alkenyl chain, or an alkynyl chain; and X covalently bonds to the surface of the inorganic substrate by a covalent bond;

depositing an organic semiconductor material directly on a surface of the organic monolayer, the organic semiconductor material being substantially free of doping; and

disposing a conductive electrode directly on at least on a portion of the organic semiconductor material;

wherein the organic semiconductor material comprises an electron blocking or a hole transport material when the inorganic substrate comprises an n-type inorganic material, and the organic semiconductor material comprises a hole blocking or electron transport material when the inorganic substrate comprises a p-type inorganic material.

2. The method of claim 1 , wherein the inorganic substrate comprises silicon.

3. The method of claim 1 , wherein the etching of the native oxide comprises etching with hydrofluoric acid (HF).

4. The method of claim 1 , wherein Y has about 4 to about 21 carbons.

5. The method of claim 1 , wherein the organic monolayer has a thickness in a range from about 0.5 nanometers (nm) to about 5 nm.

6. The method of claim 1 , wherein forming the organic monolayer on the surface of the inorganic substrate further comprises heating the inorganic substrate in the presence of a compound having the following formula: HX—Y.

7. The method of claim 6 , wherein the heating is performed at a temperature in a range from about 90 to about 150° Celsius (° C.).

8. A method for inorganic passivation in a photovoltaic device, the method comprising:

etching a native oxide over an inorganic substrate, the inorganic substrate comprising silicon and having a surface;

forming an organic monolayer directly on the surface of the inorganic substrate to form a silicon heterojunction, the organic monolayer having the following formula:

˜X—Y—Z,

wherein X is an oxygen or a sulfur; Y is an alkyl chain, an alkenyl chain, or an alkynyl chain; Z is a methyl group or an epoxy group; and X covalently bonds to the surface of the inorganic substrate by a silicon-oxygen bond or a silicon-sulfur bond;

depositing an organic semiconductor material directly on a surface of the organic monolayer, the organic semiconductor material being substantially free of doping; and

disposing a conductive electrode directly on at least on a portion of the organic semiconductor material;

wherein the organic semiconductor material comprises an electron blocking or a hole transport material when the inorganic substrate comprises an n-type inorganic material, and the organic semiconductor material comprises a hole blocking or electron transport material when the inorganic substrate comprises a p-type inorganic material.

9. The method of claim 8 , wherein the Y is an alkenyl chain comprising all cis double bonds or all trans double bonds.

10. The method of claim 8 , wherein Y is substantially free of branching.

11. The method of claim 8 , wherein the silicon heterojunction is further processed to form a portion of a photovoltaic device.