Concentrator Photovoltaic installations

based on III-V-heterostructure solar cells

V.M.Andreev Head of Photovoltaics Laboratory of the Ioffe Physical-Technical Institute,

26 Polytekhnicheskaya str. 194021, Saint-Petersburg, Russia

Phone: (812)297-5649 Fax (812)297-1017

e-mail: vmandreev@mail.ioffe.ru, http://pvlab.ioffe.ru

Solar cell chip with

dimensions of

2 mm x 2 mm

Concentrator module

0.5 m x 0.5 m based

on 144 submodules

Concentrator PV array (1m2)

based on 576 submodules

Concentrator PV installation

based on 2592 solar cells and

Fresnel lenses

http://www.ioffe.ru

http://pvlab.ioffe.ru

Early developments of III-V-heterostructure solar cells and PV

installations at the PV Lab of Ioffe Institute

Solar cells based on AlGaAs/GaAs heterostructures were at first proposed and fabricated at the Ioffe

Institute in 1969 under the direction of Prof.Zh.I.Alferov. Owing to their higher efficiency and improved

radiation hardness, nanoheterostructure solar cells are used widely in space. Heterostructure solar

cells with total area of 70 m2, fabricated at the Enterprise “Kvant” using technology developed at the

Ioffe Institute, were installed on the Russian space station “Mir” and on the other spacecrafts.

“Mir” station with two

wings equipped with

heterostructure solar

cells

Module with

small (1cm2)

lenses (1989)

CPV installation based on

mirrors (1981).

Rightmost: Prof. Zh.Alferov,

Nobel Prize laureate

CPV installation

based on Fresnel

lenses (1986)

Terrestrial concentrator PV installations developed at Photovoltaics Laboratory (http://pvlab.ioffe.ru)

of the Ioffe Institute since 1980 consist of concentrator photovoltaic modules arranged on sun

trackers. The advanced concentrator module consists of a frontal concentrator panel, which is a

parquet of Fresnel lenses, and a rear power generating plate, on which multijunction (MJ) solar cells

with secondary concentrating optical elements are placed in the focal points of the lenses.

pAl0.8Ga0.2As

p+GaAs

p-GaAs

n-GaAs

n-GaAs/AlAs

12 periods

1 m μ n-GaAs

GaAs- n++

Contact layer

AlInP-n Window

GaInP-n Emitter

GaInP-p Base

(Al)GaInP- p+ BSF

Tunnel Junction

Tunnel Junction

AlGaAs- n Window

GaInAs- n Emitter

GaInAs- p Base

(Al)GaInP- p+ BSF

Tunnel Junction

Tunnel Junction

GaInAs- n Buffer

GaInP- n Window

n-Ge junction

р-Ge – substrate

GaInP/GaAs/Ge 3J cell structure

MOCVD installation AIX200/4 for

fabrication of multijunction solar cells

0.5 m μ

p+ GaAs p-AlGaAs n-GaAlAs

p n Bragg

reflector

n+ GaAs

GaAs AlAs/GaAs

SEM and STM images of AlAs/GaAs Bragg Reflector –

part of multijunction solar cells

GaInP/GaAs/Ge 3J solar cell developed at IOFFE Institute

n-AlInP “window”

n-InGaP emitter

p-InGaP base

p-AlInP BSF

GaAs

средни

й элеме

нт

(1,40 eV)

Reduction of optical losses:

grid contact, antireflecting

coating

Reduction of losses

at the interfaces by

using tunneling

p-n junctions

Reduction of contact

losses

Reduction of losses from

the charge carrier surface

recombination

Reduction of bulk

recombination losses:

rear barriers

Matching of the lattice

parameters and

application of

nanodimensional layers

Limitation of charge

carriers

Reflection of photons

Matching of photocurrents

n-InGaP “window”

n-GaAs emitter

p-GaAs base

p-InGaP BSF

n-Ge emitter

Conversion of the

short-wavelength part

(400-670nm) of the solar

spectrum

Conversion of the

middle-wavelength part

(670-900nm) of the solar

spectrum

Conversion of the

IR part (900-1650nm) of

the solar spectrum

p-Ge base

Sunlight

1 ?

m

20 nm

III-V multijunction solar cell technology at Ioffe Institute

SIMS distribution of elements: P, As, In, Al, Ga, Zn, C, Si in

AlGaInP/GaInP/GaAs tandem cell structure

0 200 400 600 800 1000 1200 14001E14

1E15

1E16

1E17

1E18

1E19

1E20

1E21

1E22

1E23

ZnZn

Al

Zn

AsGa

n-G

aA

s

(ba

se

)

p-A

lGa

As

p-G

aA

s

n-G

aIn

P

p-G

aIn

P

p-A

lGaIn

P

p+ G

aA

s

Al

Al Al

P

In

C

ZnSi

Si

Zn

Zn

As

As

In

In

P

Ga

Ga

P

Al

Ga

In

As

P

Zn

C

Si

Concentr

ation o

f ato

ms, cm

-3

Thickness, nm

Al

Si

i-G

aIn

P

n+ GaAs p+ GaAs

C

Demonstration of > 35% efficiency at

500-800 suns in the TJ GaInP/GaAs/Ge

cell with dimensions of 2x2 mm2

Efficiency of the triple-junction

InGaP/InGaAs/Ge solar cell as a function of

temperature at different illumination

conditions (1 sun and 800 suns)

Photoresponse data for triple-junction

GaInP/GaAs/Ge nanoheterostructure

concentrator solar cell with efficiency >36%.

Characteristics of triple-junction GaInP/GaAs/Ge cells

1 10 100 10002,2

2,4

2,6

2,8

3,0

3,2

606468727680848892

Concentration, X

Efficiency

Uх.х.,V

F

F, %

FF

Uх.х.

20

22

24

26

28

30

32

34

36

38

Eff

icie

ncy,%

High temperature stability of concentrator TJ

solar cells.

Temperature coefficient (КТ = 1,5·10-3 ºС-1) of TJ

cell efficiency in three times lower than in silicon

cells.

-50 0 50

30

35

40

45

1 sun

800 suns

Eff

icie

nc

y (η

), %

Cell temperature (T) , ºC

-25 25

KT = 1.5·10-3

ºC-1

400 600 800 1000 1200 1400 1600 18000

20

40

60

80

100

Qu

an

tum

effic

ien

cy, %

Wavelength (), nm

GaInP GaAs Ge

Concentrator modules based on Fresnel lens parquets with

low aperture submodules

A section of a module structure (“all-

glass” design) based on 2 Fresnel lenses

and 2 multijunction solar cells

The tendency in

concentrator PV:

from large to small

concentrators at high

concentration ratio!

Front glass sheet

Fresnel lens profile made of silicone

Solar cell

Bypass diode Copper trough

Upper contact strip

Channel for silica

gel

Rear glass sheet

Advantages of the small-aperture

(16cm2) concentrator sub-modules:

- lower ohmic losses in the small-

area (2-4 mm2) solar cells

- no necessity in compensation of

thermal expansion difference

between materials of a solar cell

and heat sink

- reduced (to 7 cm) thickness of a

module

- lower consumption of the module

housing and heat sink materials.

CPV module (0.5 x 1 m2) based on 288 sub-modules (4cm x 4cm

each) with efficiency exceeding 26% (AM1.5) 7 concentrator modules

(0.5m x 0.5m) based on

144 mini modules each

Rays from Fresnel

lens

Rear glass

sheet

Secondary lens

Solar cell

Heat sink

Design of the submodule with

primary Fresnel lens (is not shown)

and secondary convex lens.

Misorientation angle (± W0.9, curve 1) and maximum local

sunlight concentration (Cmax, curve 2) vs. focal distance of

secondary lenses for PV submodule with 40 x 40 mm2

Fresnel lens and solar cell diameter da = 1.7 mm (without

glass kaleidoscope).

Glass kaleidoscope

Secondary lens

Design of submodule with “short focus” convex

lens and with additional kaleidoscope glued on

the cells surface and providing the uniformity of

the cell illumination

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,40,6

0,7

0,8

0,9

1,0

Photo

curr

ent,

rel. u

nits

Misorientation angle, degrees

without

secondary

lens

f = 5 mm

f = 11 mm

f = 26 mm

The results on misorientation angle measurements

for a PV sub-module with 40x40 mm2 primary

Fresnel lens, a solar cell 1.7 mm in diameter and

secondary lenses of different focal distances f

(without glass kaleidoscope).

Misorientation characteristics of CPV submodules

0 4 8 12 16 20 24

0

1

2

3

4

5

6

7

8

9

10

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

Maxim

al lo

cal concentr

ation C

ma

x,

10

3suns

Focal distance of secondary lens, mm

1

2

Mis

orie

nta

tio

n a

ng

le,

W 0

.9,a

ng

le

Concentrator PV installations developed at Ioffe Institute

1 kWp

Tower type tracker, front side of array Back side of array

Carousel type tracker, 1 kWp array Concentrator (2 bottom rows) and Si-

type (3 top rows) PV modules, 5 kWp

Advantages of concentrator PV installations based on III-V-heterostructure

solar cells

• Efficiency exceeding 35% in multijunction solar cells at conversion of concentrated sunlight.

• Intermediate concentration (up to 800x) of the sunlight by means of the Fresnel lenses (with optical

efficiency as high as 87%) and proportional decrease in solar cell area and cell specific cost.

• Low temperature coefficient of efficiency: KT = -1/η·dη/dT = 1.5·10-3 ºC-1 – three times less than in the

silicon based modules.

• More than in 2 times increase in electric power amount generated by the concentrator array.

• 1 gram of semiconductor material in a CPV installation provides the same amount of electricity that

provides by 5 tons of petroleum.

• Energy payback time of the developed CPV installations is less than 1 year.

• Decrease in two-three times the quantity of consumable materials (glass sheets, metal components

for modules and trackers, electrical cables and square of land) necessary for CPV installations.

• Predicted specific cost of CPV systems is less than $1.5/Wp at production capacity exceeding

100MWp/year.

10 kW CPV system based on carousel roof-top tracker

design equipped with 30 modules (0.5m x 0.5m each) Scheme of CPV system based on tower-type

tracker with 60 modules (0.5m x 1m each)

Project ROSSOL “Organizing the production of concentrator photovoltaic installations based on nano-heterostructure solar cells”

supported by RUSNANO www.rusnano.com/Post.aspx/Show/24310

• Goal: production of new generation CPV modules with multijunction solar cells,

Fresnel lenses and tracking systems

• Products: Photovoltaic installations with capacity: 3 and 6 kW

• Investment: Total – €125 mln, RUSNANO – €30 mln

• Production volume – 95 MW/year installations

Front surface of solar cells for 1000 suns

CPV module (0.5m x 1m) proposed for production

There is the part of the funds to finance it, and confidence in sales of the

product is very important. Thus we are looking for partners for this project which

has an access to one of the key solar markets.

Concentrator installation

Intellectual property of Ioffe Institute in CPV area

Presence of copyrights:

Priority developments of heterostructure SCs from 1969:

Nobel Prize of Zh. Alferov, technologies, publications, innovation certificates.

Priority developments of concentrator modules based on sun-tracking systems from

1981: publications, technologies, patents.

Priority developments of solar power installations with sun-tracking systems from

1979.

Total number of patents, which are planned to use in the Project, right on which are

possessed by the Ioffe Institute, is 48.

The Ioffe Institute proposes to use 48 know-hows in realizing the Project.

Single-lamp (on the left) and four-lamp (on the right)

flash testers for 3-J solar cells (5000 X)

Testing equipment developed at Photovoltaics laboratory

(http://pvlab.ioffe.ru) of the Ioffe Institute

Colimated light flux

with divergence of 32’

at 1 sun intensity

generated by four

flash lamps.

CPV module aperture

up to 0.5m x 1m

Flash testers were delivered to NREL, Spectrolab (USA), Fraunhofer Institute for Solar Energy

Systems (Germany), SolarTech (Germany), Ricerca Sistema Energetico (Italy), TIPS (China) and

6 Flashers to Russian companies.

Flash tester for MJ solar cells Flash tester for CPV module

Milestones of the future developments

and subjects for cooperation

• Creation of the new generation of CPV installations based on R&D:

- III-V heterostructure solar cells with efficiencies >40% at 1000 suns

- new design and technology of concentrator PV modules with efficiency

~35%

- new design of solar trackers with tracking accuracy of 0.1 angle degree

- new generation of PV systems based on heterostructure solar cells and

concentrators

- monitoring and aging the solar cells, modules, trackers and CPV

systems

• Technologies transfer to partner(s) and organizing the high scale

production of CPV installations with using the developed technologies

- achieving the prognosticated life time >25 year of modules and installations

- providing energy payback time < 1 year

- achieving the cost of CPV system installed power of < €1.5/Wp