High Work Function MoO2 Back Contacts for Improved Solar Cell Performance

Patent metadata

Field	Value
Publication number	US-2018226524-A1
Application number	US-201715425717-A
Country	US
Kind code	A1
Filing date	Feb 6, 2017
Priority date	Feb 6, 2017
Publication date	Aug 9, 2018
Grant date	—

Abstract

Improved high work function back contacts for solar cells are provided. In one aspect, a method of forming a solar cell includes: forming a completed solar cell having a substrate coated with an electrically conductive material, an absorber disposed on the electrically conductive material, a buffer layer disposed on the absorber, a transparent front contact disposed on the buffer layer, and a metal grid disposed on the transparent front contact; removing the substrate and the electrically conductive material using exfoliation, exposing a backside surface of the solar cell; depositing a high work function material onto the back side surface of the solar cell; and depositing a back contact onto the high work function material. A solar cell formed by the present techniques is also provided. Yield of the exfoliated device can be improved by removing bubbles from adhesive used for exfoliation and/or forming contact pads to access the metal grid.

First claim

What is claimed is:

1 . A method of forming a solar cell, the method comprising:
forming a completed solar cell comprising a substrate coated with an electrically conductive material, an absorber disposed on the electrically conductive material, a buffer layer disposed on the absorber, a transparent front contact disposed on the buffer layer, and a metal grid disposed on the transparent front contact; removing the substrate and the electrically conductive material using exfoliation, exposing a backside surface of the solar cell; depositing a high work function material onto the back side surface of the solar cell; and depositing a back contact onto the high work function material.

2 . The method of claim 1 , wherein the absorber comprises copper, zinc, tin, and at least one of sulfur and selenium.

3 . The method of claim 1 , wherein the absorber has a thickness of from about 0.5 μm to about 2 μm, and ranges therebetween.

4 . The method of claim 1 , wherein the high work function material comprises molybdenum dioxide.

5 . The method of claim 1 , wherein the back contact comprises a metal selected from the group consisting of: gold, platinum, silver, and combinations thereof.

6 . The method of claim 1 , further comprising:
attaching a handle substrate to a top surface of the solar cell.

7 . The method of claim 6 , wherein the handle substrate comprises a fused silica plate.

8 . The method of claim 6 , wherein the handle substrate is attached to the top surface of the solar cell using an epoxy, the method further comprising:
preparing the epoxy under a vacuum to prevent formation of bubbles in the epoxy.

9 . The method of claim 8 , further comprising:
spinning the epoxy in a centrifuge to remove bubbles from the epoxy.

10 . The method of claim 1 , further comprising:
forming a via in the solar cell by selectively removing a portion of the solar cell down to the electrically conductive material.

11 . The method of claim 10 , further comprising:
forming a patterned mask on a top surface of the solar cell; and depositing a contact metal, through the patterned mask, into the via forming a through contact in the via.

12 . The method of claim 11 , wherein the contact metal is selected from the group consisting of: nickel and aluminum.

13 . The method of claim 11 further comprising:
depositing the contact metal, through the patterned mask, forming a contact pad connecting the through contact to the metal grid.

14 . The method of claim 1 , further comprising:
smoothing the backside surface of the solar cell after the substrate and the electrically conductive material have been removed.

15 . The method of claim 14 , wherein the smoothing is performed using a wet etch.

16 . The method of claim 15 , wherein the wet etch comprises bromine methanol.

17 . A solar cell comprising:
a back contact; a high work function material disposed on the back contact; an absorber disposed on the high work function material; a buffer layer disposed on the absorber; a transparent front contact disposed on the buffer layer; and a metal grid disposed on the transparent front contact.

18 . The solar cell of claim 17 , further comprising:
a via in the solar cell that extends down to the high work function material.

19 . The solar cell of claim 18 , further comprising:
a through contact in the via.

20 . The solar cell of claim 19 , further comprising:
a contact pad connecting the through contact to the metal grid.

Assignees

• IBM

Inventors

• Antunez Priscilla D
• Bishop Douglas M
• Fraczak Gloria W
• Gunawan Oki
• Haight Richard A

Classifications

• Y02E10/50

  Photovoltaic [PV] energy · CPC title

• H01L31/022466

  Electricity · mapped topic

• H01L31/0326

  Electricity · mapped topic

• H01L31/022433

  Electricity · mapped topic

• H01L31/022441 Primary

  Electricity · mapped topic