Unique a-Si solar cells and advanced PV systems

Journal of Non-Crystalline Solids 115 (1989) 189-194 North-Holland

189

Section 11: Solar cells H

UNIQUE a-Si SOLAR CELLS AND ADVANCED PV SYSTEMS

Yukinori Kuwano, Masao Isomura Functional Materials Research Center, SANYO Electric Co., Ltd. 1-18-13, Hashiridani, Hirakata-City, Osaka, Japan

A-Si solar cells have been significantly improved through research, technology and industrialization in a mere ten years. Now, they are entering a new area, moving from consumer use to power use. In this paper, the trends of R&D and recent progress in a-Si solar cells are reviewed, and unique a-Si solar cells and advanced PV systems are introduced.

I. INTRODUCTION The

use

source

of

petroleum

fuels

as

an

energy

is causing a number of serious problems _

that

are

year

by

degrading year.

pollution

For

rain.

global

example,

generated

consumed,

the

when

is

dissolved

in

damage

that

on

serious.

a

CO 2

the

atmospheric

petroleum

The

ecosystems

environment

world

rain

fuels

to

this

scale

concentration

form

is

4.0 '~

E

3.0 -~

acid to

400

¢q

8

2.0 200

extremely

also

_

are

causes

is

_

600

rising

"LO ~

0 I

at a rate of 1 ppm per year with the increase in

fuel

the a

consumption,

"greenhouse variety

continues

of

abnormal

unabated,

in temperature scale

by

the

thereby

effect"

we

and

phenomena. will

be

of

the

If

Against

century,

as PV

and

this

background,

increasingly

clean

energy

solar

promoted source,

as

and

energy

a

is

the

available

are

introduced

development

of

Among

Since

for solar cells,

1975

succeeded has

in

received

when

valency much

semiconductor material.

lower

1976

benefit

has

motivated

In

paper,

progress and

in

unique

the

a

great

trends

of

a-Si

solar

cells

a-Si

solar

cells

This

deal R&D

real

of

and

are and

R&D.

recent

reviewed, advanced

0022-3093/89/$03.50 © Elsevier Science Publishers B.V. (North-Holland)

first

when

Carlson

a-Si

efforts

solar

have

technologies. promotion

of

and of

attention

of

costs.

Spear control

because

this

a

solar

2. A TREND OF R&D AND RECENT PROGRESS

amorphous Si (a-Si) has received much attention fabrication

for

limitless

has rapidly expanded.

many materials

systems

energy age.

solar cells that can convert sunlight directly into electricity

I

FIGURE 1 Prediction of increase in CO 2 concentration and surface temperature (Edmonds-Reilly model)

this

shown in Fig. i.

being

I

2080

Year

on a global

21st

I

2040

about

facing a rise

and serious danger middle

I

2000

intensifying

bringing

~

LeComber

a-Si (I), as

a

In particular,

it new

since

and Wronski reported the (2) cell , intensive research

concentrated on a-Si solar cell In the

Japan, Sunshine

the

accelerative

Project

by

NEDO

190

Y. lt uwano, M. Isomura / Solar cells and advanced P V systems

poly-Si (New

Energy

and

Development

Organization)

research.

In

projects the

Industrial

the

have

U.S.

been

Commission

of

respectively.

In

by

a-Si

solar

by

SANYO

for

have

and

intensified

Europe,

promoted

by

1980,

similar

the

European

cells

DOE

500

and /

Communities,

calculators

were

put

on

100

powered

the

c-Si~

market

solar

sources

rapidly

of

all

since

cells

have

been

used

as

power

products.

The

various

in

consumer of

cells

area

the

which

cell In

a-Si

in

1987,

solar

of excellent large

and

increasing

2 (3).

solar

time,

volume

MWp

Fig.

first

for

production

10.7

the

world

future,

features,

as

to

increase

exceeding

O

13.9/

fabrication

/

~ t ~ . 0 ~"

poly-Si

of

in

1

a-Si

I I ! I I I I

1983 85

I

I

88 90 95 Calendar year

2000

because FIGURE 2 share of solar

such as their low cost,

simple

/ /

37.4%

shown

production

^ c-Si

/ /

0

o

for

/

/

(20MW)~

•.~ 10

is

cells

accounted

production,

is expected

and

solar

E -6 >

then

/

/

Production share

¢,

a-Si

1983

Technology

Production the world

process.

cells

in

HIGH EFFICIENCY CELLS I

KEY FACTOR FOR TECHNOLOGY OF a-Si CELLS I-tgh quality Hayer \ Photovoltaicdoped layer~ /New narrow gap material /

I

Fut

/

(11)(12) P: pc-SIC solar cell~ (10)~ Multi-bandgap structure

(7)~

Laser patterningmethod ~ Optical confinemeotstructur(eS~___.] P:a-SIC window lay(4) -

Consecutiveseparated chamb(8)

-

~ J

~.

~ _ _~9~Of

Large scale/residential power supply , New effective applications

~ Roofingtile (Model house) /____, See-through solar cell

1 9 8 ~

Sunroof

~ Radio yBattery charger ~ 2kWsystem ~ > Watch ~ F i r s t industrializationfor calculator

Integrated type cell First a-SI Valency corttrol(1)E:

I KEY FACTOR FOR APPLICATION

FIGURE 3 Trends and concepts behind cell R&D

a-Si solar

Y. Kuwano, M. Isomura/Solar cells and advanced PV systems

Fully utilization of characteristic features of a-Si

191

Real solar energy age

Ircident llght

Roofing tile

Trar~t~

through cell

Stand-alone systems

Sdar gukJe post

Middle-scale systems Sdar cell sunroof

Rexble

I

Pumping ~ - - sys,tern TV system

Creation of inter

tte demand for real solar energy age step by step Street lamp Creation of suitable markets for a-Si solar cells

Consumer Products

FIGURE 4 Strategy For the develoDment of applications of a-Si solar cells

the

192

Y. Kuwano, M. Isomura / Solar cells and advanced PV systems

A great deal of time and effort has been spent developing

a-Si

positive a-Si

solar

in

the

to an market

has

systems. behind

the

Fig.

been

the

The

progressing of

a

Q 2nd. back electrode ~) insulator

PV

1st. back electrode

the world's energy

unique

applications

developed,

market.

the

for

a-Si

leading

TCO ...

The extended

development

of

PV

~) g l a s s -

3 shows the trends and concepts

development

of

technologies

example,

is

have of

numerous

realization

Many

boosted

the

Various for

cells

extension

and

obtained.

of supplying

future.

solar

been

development

towards

system capable

cells,

have

cell

favorably

a-Si

solar

results

SiC

a-Si

solar

cells. FIGURE 5 Structure of the THC integrated-type a-Si submodule

have

been developed, (4) layers , the super

window

chamber (5), optical confinement structures (6), and

the

have

laser

improved

cells

and

patterning the

method 17)" "

performance

created

unique

of

These

were

solar

for

a-Si

applications

at each

marketed a-Si

various

pumping 3. UNIQUE a-Si SOLAR CELLS AND THEIR EXCELLENT

The

excellent

possible with

new

solar

features

create

has

output this

in

patterning

this

However,

laser

patterning

structure,

Our

developed,

strategy

in

Fig. a-Si

in

pocket

powered Later,

for

4.

by

cells

cell

is For

metal

and

patterning has

mask

conventionally method,

been

the

developed

area and to fabricate

Other

unique

based

on this structure.

world's to

calculators

marketed

radios,

and

a-Si

a-Si

is

first

consumer

integrated-type

watches,

solar

substrate.

applications

The

solar

a-Si

obtain a (8) substrate

were

method,

cells.

been

of

a new

the effective

large-area

a-Si one

it

cells

to

one

methods

used.

to enlarge

from

on

make

solar

integrated-type

each

series

a-Si

a-Si

developed

voltage

photolithography

have

An

been

structure,

connected

of

various

concepts.

cell

high In

to

cells

summarized application

applications

of

a

car

are

fabricated steel formed

and

a-Si

a

are

unique

a-Si

plastic

a-Si

solar

which

on a transparent

which

curved

cell

spaced

of is

or stainless

tile

a-Si

a

unique

features

cell

roofing

create creation

sunroof,

post

excellent

holes

to

A

as

These

gradual

age.

see-through

were

such

is

glass

which

has

uniformly

on

an integrated-type a-Si solar cell. Recently, Contact

we

(THC)

developed

the

integrated-type

submodule

from

technology.

As shown in Fig.

back

electrode

and

power

chargers

the

on a flexible an

modules

systems.

guide

flexible

microscopic

in

battery

a

the

directly

tile,

microscopic

cells.

solar

stage,

developed

for

energy

a

market

next

systems,

Especially,

film,

was

solar

solar and

suitable the

cell

TV

been

utilizing

a-Si

many

and

have

applications. cells

solar

demands

real

solar

a In

stand-alone

systems

products 1980

of

for

intermediate

FEATURE

create

cells.

kinds

developed

stage of development.

to

solar

about

submodules 95%.

10% by

and

to can

larger

enlarging

A.Madan

a-Si

see-through

connected

holes,

also

Through-Hole solar a-Si

cell cell

5, it has another its

TCO

obtain than

many

output

conventional

effective reported

by

an

area a

to

similar

Y. Kuwano, M. Isomura / Solar cells and advanced P V systems

193

FIGIJRE 6 Global Energy Network Equipped with Solar cells and International Superconductor grids(GENESIS)

Table 1 World's energy consumption and required solar cell system area in 2000

Primary energy consumption

Conversion efficiency of solar cell system

oil equivalent

XlO'°k~/y Total

1.404

(%)

Thermal

Electric

[A,]

[A,]

0.421

0.983

i0

Conversion factor of oil

Required solar cell

system area

(I~~ Ira' .y)

(XI0'°m ') [ ~

A~/B, +A,/B,

square]

Including a green zone

Simple

Electric

[B,]

[B,]

O. 01736

O. 04960

65. II

130.2

( n-35X)

[8073

[11413

I) Primary energy consumption in 1990 ; 180xlO'(barrel/day):l. 045xi0' °(k~/year) 2) Growth rate of primary energy consumption ; 3 %

structure,

which is not an integrated-type (13).

4. ADVANCED PV SYSTEMS OF THE FUTURE As has

previously been

a-Si

made

solar

technology

can

expect

the

to

be

will

By

power

the

system,

far

to

ten

from

cells

main

early likely form

2,000s, be

to

for

we

solar with

photovoltaic

(Global

Superconductor

Energy

9,

generated world

in

capable

order

form

to

providing

one

supplied

sunny

by

places obtain

Even

area, the

in

an

be

of

the

parts

enormous

if

it

system

countries. and

stable

is night power

superconductor

other

shown

will

consistent,

electric

sufficient

and

as

power

various

a

cells

grids),

solar

in

supply. in

can

which

constantly

of

power

be

a-Si

Solar

in

Fig.

widely serve

with

in

rain

future

Equipped

International

future

combined

a global

GENESIS

and

also

cell

source

since

However,

from

are

solar

energy

called

years

complete

developments

the

very

superconductors

mere

progress

development.

solar

essential

societies. ceils

is

major

considerable

the

first

a-Si

expected as

in

cells

the

research,

noted,

Network

or

can grid So

permanent

on

still from

people energy

without pollution anytime,anywhere. Finally, energy order

that

we

approximated

solar

to meet

the

cells world's

need

the

amount

of

to

generate

in

needs.

As

energy

194

a

Y. Kuwano, M. lsomura / Solar cells and advanced P V systems

result,

primary 1.404 the

we

energy x

per

2000.

On

year

would

year the

an

green

zone

ll41km)

which

is

desert

area

needs(Table

to

is

other

just 50%

only

the

world's

crude be

oil

at

cell

4%

satisfy

a 10%

x

807km

size,

of all

by

systems

807km

that

then

required

hand,

solar

area

a

if

will

efficiency,

require

(adding

that

consumption

lolOkl

conversion

x

estimate

ll41km

the

world's

our

energy

I)

5. SUMMARY a-Si

solar

as

a

clean,

so

a

great

concerning

cells new,

deal

R&D

Recent

and

industrialization

for

use

major

will be realized

to

energy

has

been

of

power

serve source,

conducted

improvements

applications

the

as

expected

limitless of

them.

performance

are

in cell

indicate

a-Si

that

solar

generating

cells systems

in the near future.

(New

work Energy

Development Sunshine

is

supported and

Project

part

Industrial

Organization)

International

in

under

as

a

the

Trade and Industry.

i. W. E. Spear and P. G. LeComber, State Commun., 17 (1975) 1198 2. D. E. Carlson and C. R. Wronski: Phys. Lett., 28 (1976) 671 3. Photovoltaic 1988

Solid

Appl.

News, Vol. 7, No.2, Feb.

4. Y. Tawada et. al. 53 (1981) 5273

Appl. Phys. lett.,

5. S. Tsuda et. al. 25 (I) (1987) 33

Jpn. J. Appl. Phys.,

6. S. Nakano et. al. 70, (1986) 551

Mat. Res. Symp. Vol.

7. S. Nakano et. al. 25 (1986) 1936

Jpn. J. Appl. Phys.,

8. Y. Kuwano et. al., Proc. 14th IEEE photovol. Spec. Conf., (1980) 698 9. Y. Kuwano et. al., Proc. 15th IEEE photovol. Spec. Conf., (1980) 698 I0. Y. Yukimoto et. al., Spring Meet of Jpn. Soc. Appl. Phys., (1983) 3P-A-6

ACKNOWLEDGMENTS This

REFERENCES

by

NEDO

Technology part

of

the

Ministry

of

ii. Y. Hattori et. al., Tech. Digest 3rd Int. PVSEC, Tokyo (1987) 171 12. Y. Kuwano et. al., MRS Spring meeting, USA (1988) 13.

J. Xi (1987)

et.

al.,

3-rd

Int.

PVSEC,

Tokyo