Photovoltaic Devices with Textured TCO Layers, and Methods of Making TCO Stacks

Patent metadata

Field	Value
Publication number	US-2022013674-A1
Application number	US-201917279254-A
Country	US
Kind code	A1
Filing date	Sep 23, 2019
Priority date	Sep 24, 2018
Publication date	Jan 13, 2022
Grant date	—

Abstract

According to the embodiments provided herein, a method for sputtering a TCO material onto a substrate includes process conditions that produce a textured topography at the interfaces of various layers. The textured topography can include an average roughness from about 5 to about 40 nm. The process conditions can include providing oxygen in the sputtering environment at a flow rate of from 0 to about 30 sccm; or heating the substrate to at least 200; or increasing the magnetic field strength to above 40 mT. The textured topography creates interfacial transition areas which have hybrid physical properties compared to their constituent materials.

First claim

What is claimed is:

1 . A method for manufacturing a thin film transparent conductive oxide layer stack, comprising:
sputtering onto a substrate at least one transparent metal oxide layer in an inert sputtering environment; controlling the inert sputtering environment with oxygen at a flow rate of from about 0.1 sccm to about 30 sccm to produce a sputtered transparent conductive oxide layer stack that has at least one interface having an average roughness from about 5 nm to about 60 nm; and annealing the transparent conductive oxide layer stack.

2 . The method according to claim 1 wherein the average roughness is from about 5 nm to about 30 nm.

3 . The method according to claim 1 wherein the oxygen flow rate during sputtering is from about 1 sccm to about 20 sccm.

4 . The method according to claim 1 wherein the substrate temperature during sputtering is from about 25 to about 400° C.

5 . The method according to claim 1 , further comprising:
sputtering onto a substrate at least two transparent metal oxide layers having different refractive indices to form a transparent conductive oxide layer stack in which at least one interface between two metal oxide layers within the transparent conductive oxide layer stack or at least one interface between the transparent conductive oxide layer stack and an adjacent layer has an average roughness of 5 to 60 nm; annealing the transparent conductive oxide layer stack; and depositing an absorber layer on the transparent conductive oxide layer stack; whereby, upon annealing, the roughness of the at least one interface of the transparent conductive oxide layer stack produces a transition area of effective refractive index that is intermediate the refractive index of the two adjacent layers to form a more gradual gradient of refractive indices.

6 . The method according to claim 5 wherein at least one of the metal oxide layers is selected from indium tin oxide (ITO), zinc magnesium oxide (ZMO), and tin oxide (TO), and cadmium tin oxide (CTO).

7 . The method according to claim 6 wherein at least two of the metal oxide layers are selected from indium tin oxide (ITO), zinc magnesium oxide (ZMO), tin oxide (TO), and cadmium tin oxide (CTO).

8 . The method according to claim 6 wherein the average roughness is from about 5 nm to about 30 nm.

9 . The method according to claim 6 wherein the oxygen flow rate during sputtering is from about 0 sccm to about 20 sccm.

10 . A method for manufacturing an improved thin film transparent conductive oxide layer for use with an associated absorber layer, the method comprising:
sputtering onto a substrate one or more transparent metal oxide layers under conditions selected to produce a sputtered transparent conductive oxide layer having at least one interface having an average roughness when annealed of 5 to 60 nm, said sputtering conditions being selected from (i) supplementing an inert sputtering or annealing environment with oxygen or hydrogen, (ii) increasing the substrate temperature to a range from about 25 to about 400° C., and (iii) increasing a magnetic field strength associated with the sputtering process to a range from about 20 mT to about 100 mT; whereby, upon exposure to incident light, the roughness of the at least one interface of the transparent conductive oxide layer reduces reflection and increases light scattering transmission into the associated absorber layer.

11 . The method according to claim 10 wherein the average roughness is from about 5 nm to about 30 nm.

12 . The method according to claim 10 wherein the sputtering is done under a condition of supplementing with oxygen at a flow rate from about 0.1 sccm to about 30 sccm.

13 . The method according to claim 12 wherein the sputtering is done under a condition of supplementing with oxygen at a flow rate from about 1 sccm to about 20 sccm.

14 . The method according to claim 12 wherein the sputtering is done under a further condition of supplementing with hydrogen at up to 3% by weight of the inert environment.

15 . The method according to claim 10 wherein the sputtering is done under a condition of substrate temperature from about 25 to about 400° C.

16 . The method according to claim 10 wherein the sputtering is done under a condition of magnetic field strength from about 40 to about 90 mT.

17 . (canceled)

18 . A photovoltaic device comprising:
a substrate; a transparent conductive layer stack comprising at least two transparent metal oxide layers having different refractive indices to form a transparent conductive oxide layer stack in which at least one interface between two metal oxide layers within the transparent conductive oxide layer stack or at least one interface between the transparent conductive oxide layer stack and an adjacent layer has an average roughness of 5 to 60 nm; an absorber layer disposed on the sputtered transparent conductive layer stack; and a back contact disposed on the absorber layer; whereby the roughness of the at least one interface of the transparent conductive oxide layer stack produces an interfacial transition area having an effective refractive index that is intermediate the refractive indices of the two adjacent layers to form a more gradual gradient of refractive indices.

19 . (canceled)

20 . The photovoltaic device according to claim 18 wherein at least one of the metal oxide layers is selected from indium tin oxide (ITO), zinc magnesium oxide (ZMO), and tin oxide (TO), and cadmium tin oxide (CTO).

21 . The photovoltaic device according to claim 18 further comprising a barrier layer that having a refractive index that furthers the gradual gradient of refractive indices.

22 . The photovoltaic device according to claim 18 further comprising:
a substrate comprising glass having a refractive index of about 1.5;
an absorber layer comprising cadmium telluride having a refractive index of about 3; and
at least two transparent metal oxide layers disposed between them which, along with at least one interfacial transition area, define at least four interface regions between the substrate and the absorber layer, wherein the refractive indices of the at least two transparent metal oxide layers are between 1.5 and 3, such the refractive index changes by no more than 0.5 at any of the interface regions.

23 - 41 . (canceled)

Assignees

• First Solar Inc

Inventors

• Bourgeois Paulina
• Clark-Phelps Robert
• Fang Qi
• Guo Jing
• Mor Gopal
• Shao Rui

Classifications

• H10F77/484

  Refractive light-concentrating means, e.g. lenses · CPC title

• H10F71/138

  Manufacture of transparent electrodes, e.g. transparent conductive oxides [TCO] or indium tin oxide [ITO] electrodes · CPC title

• H10F77/244

  made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers · CPC title

• H10F77/247 Primary

  comprising indium tin oxide [ITO] · CPC title

• H10F77/315 Primary

  the coatings being antireflective or having enhancing optical properties · CPC title