Single heterojunction back contact solar cell

• US 8,288,645 B2
• Filed: 03/17/2009
• Issued: 10/16/2012
• Est. Priority Date: 03/17/2009
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Lee, Jong-Jan, Schuele, Paul J., Droes, Steven R.
• Primary Examiner(s): Michener, Jennifer K.
• Assistant Examiner(s): MARTIN, MATTHEW T
• Application Number:
  US12/405,962
• Publication Number:
  US 20100236613A1
• Time in Patent Office: 1,309 Days
• Field of Search: 136/252, 136/255, 136/258, 438/703, 257/E21.215, 257/E21.218, 257/E21.24
• US Class Current: 136/255
• CPC Class Codes: H01L 31/022441 Electrode arrangements specially adapted for back-contact solar cells
• CPC Class Codes: H01L 31/02363 of the semiconductor body itself, e.g. textured active layers
• CPC Class Codes: H01L 31/0682 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• CPC Class Codes: H01L 31/073 comprising only AIIBVI compound semiconductors, e.g. CdS/CdTe solar cells
• CPC Class Codes: H01L 31/0735 comprising only AIIIBV compound semiconductors, e.g. GaAs/AlGaAs or InP/GaInAs solar cells
• CPC Class Codes: H01L 31/0747 comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer
• CPC Class Codes: H01L 31/1828 the active layers comprising only AIIBVI compounds, e.g. CdS, ZnS, CdTe
• CPC Class Codes: H01L 31/184 the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
• CPC Class Codes: Y02E 10/543 Solar cells from Group II-VI materials
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02E 10/546 Polycrystalline silicon PV cells
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02E 10/549 Organic PV cells

Abstract

A back contact single heterojunction solar cell and associated fabrication process are provided. A first semiconductor substrate is provided, lightly doped with a first dopant type. The substrate has a first energy bandgap. A second semiconductor is formed over a region of the substrate backside. The second semiconductor has a second energy bandgap, larger than the first energy bandgap. A third semiconductor layer is formed over the first semiconductor substrate topside, moderately doped with the first dopant and textured. An emitter is formed in the substrate backside, heavily doped with a second dopant type, opposite of the first dopant type, and a base is formed in the substrate backside, heavily doped with the first dopant type. Electrical contacts are made to the base and emitter. Either the emitter or base is formed in the second semiconductor.

Claims

1. A method for fabricating a single heterojunction solar cell, the method comprising:

providing a first semiconductor substrate lightly doped with a first dopant type, the substrate having a topside, a backside, and a first energy bandgap;

forming a second semiconductor overlying a region of the substrate backside, the second semiconductor having a second energy handgap, larger than the first energy handgap;

forming a third semiconductor layer overlying the first semiconductor substrate topside, moderately doped with the first dopant;

texturing a top surface of the third semiconductor layer;

forming a single heterojunction as follows;

forming a first electrode element selected from a group consisting of an emitter and a base in the substrate backside, where the emitter is heavily doped with a second dopant type, opposite of the first dopant type, and where the base in heavily doped with the first dopant;

forming a second electrode element selected from the group consisting of the base and the emitter in the second semiconductor, wherein the second electrode element consists of the base or emitter unselected in the first electrode;

forming a first electrical contact to the emitter; and

,

forming a second electrical contact to the base.

2. The method of claim 1 wherein providing the first semiconductor substrate includes providing a substrate material selected from a group consisting of single crystalline silicon, multicrystalline silicon, polycrystalline silicon, amorphous silicon, single crystalline silicon-germanium, and III-V compound semiconductors.

3. The method of claim 1 wherein forming the second semiconductor and third semiconductor layer includes forming each with a material selected from a group consisting of hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, hydrogenated amorphous silicon germanium, hydrogenated microcrystalline silicon oxide, microcrystalline silicon, III-V compound semiconductors, II-VI compound semiconductors, and organic semiconductors.

4. The method of claim 1 further comprising:

heavily doping a region of the substrate backside with the first dopant;

wherein forming the second semiconductor includes depositing a second semiconductor in-situ doped with the second dopant;

wherein forming the emitter includes forming the emitter in the second semiconductor; and

,

wherein forming the base includes forming the base in the heavily doped region of the substrate backside.

5. The method of claim 1 further comprising:

heavily doping a region of the substrate backside with the second dopant;

wherein forming the second semiconductor includes depositing a second semiconductor in-situ doped with the first dopant;

wherein forming the base includes forming the base in the second semiconductor; and

,

wherein forming the emitter includes forming the emitter in the heavily doped region of the substrate backside.

6. The method of claim 1 wherein forming the second semiconductor includes depositing a second semiconductor using a process selected from a group consisting of chemical vapor deposition (CAM), plasma enhanced chemical vapor deposition (PECVD), hot wire chemical vapor deposition (HWCVD), high frequency plasma enhanced chemical vapor deposition (HFPECVD), high density plasma enhanced chemical vapor deposition (HDPECVD), inkjet printing, and screen printing.

7. The method of claim 1 further comprising:

selectively forming thermal oxide overlying the substrate backside;

heavily doping regions of the substrate backside exposed through openings inn the thermal oxide;

forming a SiNx film overlying the substrate top surface and the heavily doped regions of the substrate backside;

etching exposed regions of thermal oxide;

depositing the second semiconductor through the etched openings in the thermal oxide overlying the substrate backside.

8. The method of claim 1 wherein forming the third semiconductor layer includes forming the third semiconductor layer selected from a group consisting of depositing a third semiconductor layer, moderately doped with the first dopant, overlying the first semiconductor substrate topside, and doping the topside of the first semiconductor substrate.

9. The method of claim 1 wherein providing the first semiconductor substrate lightly doped with the first dopant type includes providing an n-doped silicon substrate;

and,

wherein forming the base in the substrate backside, heavily doped with the first dopant type, includes forming an n+ doped base in an amorphous silicon second semiconductor material.

10. A single heterojunction solar cell, the solar cell comprising:

a first semiconductor substrate lightly doped with a first dopant type, the substrate having a topside, a backside, and a first energy bandgap;

a second semiconductor film overlying a region of the substrate backside, the second semiconductor having a second energy bandgap, larger than the first energy bandgap;

a third semiconductor layer with a textured top surface, overlying the first semiconductor substrate topside, moderately doped with the first dopant;

a single heterojunction comprising;

a first electrode element selected from a group consisting of an emitter and a base formed in the substrate backside, where the emitter is heavily doped with a second dopant type, opposite of the first dopant type, and where the base is heavily doped with the first dopant;

a second electrode element selected from the group consisting of the base and the emitter in the second semiconductor, wherein the second electrode element consists of the base or emitter unselected in the first electrode;

a first electrical contact to the emitter; and

,

a second electrical contact to the base.

11. The solar cell of claim 10 wherein the first semiconductor substrate is material selected from a group consisting of single crystalline silicon, multicrystalline silicon, polycrystalline silicon, amorphous silicon, single crystalline silicon-germanium, and III-V compound semiconductors.

12. The solar cell of claim 10 wherein the second semiconductor film and third semiconductor layer are each a material selected from a group consisting of hydrogenated amorphous silicon, hydrogenated amorphous silicon carbide, hydrogenated amorphous silicon germanium, hydrogenated microcrystalline silicon oxide, microcrystalline silicon, III-V compound semiconductors, II-VI compound semiconductors, and organic semiconductors.

13. The solar cell of claim 10 wherein the substrate backside includes a region heavily doped with the first dopant;

wherein the second semiconductor film is heavily doped with the second dopant;

wherein the emitter is formed in the second semiconductor film; and

,

wherein the base is formed in the heavily doped region of the substrate backside.

14. The solar cell of claim 10 wherein the substrate backside includes a region heavily doped with the second dopant;

wherein the second semiconductor film is heavily doped with the first dopant;

wherein the base is formed in the second semiconductor; and

,

wherein the emitter is formed in the heavily doped region of the substrate backside.

15. The solar cell of claim 10 wherein the third semiconductor layer is selected from a group consisting of a separate semiconductor layer, moderately doped with the first dopant, deposited over the first semiconductor substrate topside, and a moderately doped region topside region of the first semiconductor substrate.

16. The solar cell of claim 10 wherein the first semiconductor substrate is a lightly n-doped silicon substrate;

and,

wherein the base is a heavily n+ doped amorphous silicon second semiconductor material.