ANU College of

Engineering & Computer Science

Applications of Sputtering to Silicon Solar Cells By Xinyu Zhang, ANU Research School of Engineering, xinyu.zhang@anu.edu.au Supervisors: Professor Andres Cuevas, Dr. Andrew Thomson

1 Introduction

Photovoltaic solar energy is believed to be an attractive alternative for

future’s energy consumption. Since the first silicon solar cell was

developed in 1954 [1], solar energy has been continuously competing with

other energy resources. As a result, the “cost of solar power” is always the

main theme in the history of solar cells, and it will guide future research

directions as well.

2 Motivation

There are two ways of reducing solar power cost by

improving solar cells:

Improve solar cell Reduce manufacturing costs

Time Solar Power

Cost

Applications Achievement

1950s

~

1970s

~ 300 $/W Only cost-effective in space

applications.

1970s

~

1980s

100 $/W

→ 10 $/W

Thanks to the developments of

screen-printing technique and

solar panels, cost was greatly

reduced. Applications in remote

areas become competitive with

power.

1990s ~

Today 10 $/W

→ 2 $/W

Incredible development for solar

industry [2]:

• Growth rate over 44% per year.

• Global cumulative installed

capacity over 70 GW in 2011.

In the

future

“solar energy could provide a

third of the global final energy

demand after 2060”

-- International Energy Agency

2011 [3]

Lab made solar cells:

• High efficiency

• Expensive to make

Industrial solar cells:

• Relative low efficiency

• Cheap to make

Cost-effective techniques for higher efficiency solar cells are

required, and sputtering creates the potential to achieve this.

3. Background

Advantages of sputtering:

• Large-scale processing

systems available

• Non-toxic; non-explosive

and easy-produced target

source

• Low temperature process

• Relatively cheap

RF Power

4. Research objects and initial results

The main applications of sputtering in my project are:

• Surface passivation layer deposition

• Back surface field formation

• Rear contact formation

Last year’s research shown:

Sputtering conditions for AlOx surface passivation

layer deposition can be well controlled [4]

1.0 1.5 2.0 2.5 3.00

1

2

3

4

5

6

7

8

9

10

O2 flow rate (sccm)

Dep

ositio

n R

ate

(n

m/m

in)

Ar 35 sccm

Ar 30 sccm

Ar 25 sccm

Ar 20 sccm

Ar 15 sccm

Power = 300 W

Pressure = 3 mTorr

100 150 200 250 300

0

1

2

3

4

5

6

7

8

9 1 mTorr

3 mTorr

5 mTorr

Power (W)

De

po

sitio

n R

ate

(n

m/m

in)

Ar = 30 sccm

O2 = 1.6 sccm

Effective surface passivation for crystalline silicon can

be achieved [4]

5. Conclusions: Surface passivation for crystalline silicon by sputtered AlOx

films have been studied, and that is the most important

application in this project. It has been proved that effective

surface passivation can be achieved by this method. Future

work will be conducted on further study of sputtering

technique and developing other applications to solar cells.

[1] D. M. Chapin, et al. J. Appl. Phys., 25 (5), 676-677.

[2] International Renewable Energy Agency, “Solar Photovoltacs”, Vol 1 (4/5), 2012.

[3] International Energy Agency, “Solar Energy Perspectives”, 2011.

[4] X. Zhang, et al. 38th IEEE PVSC, Austin, TX, 2012.