Customised PV Cells

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Customised

Photovoltaic Cells


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Customised Photovoltaic Cells

Scientific Knowledge for Modern Applications

2 Fraunhofer ISE

The Fraunhofer Institute for Solar Energy

Systems ISE offers a variety of high-quality semi-conductor products which have resulted from

long-term research on solar cells at highest effi-

ciency values. We have developed a whole range

of cell sizes and designs for various application

areas. In addition to operational cells, we offer

our scientific know-how to implement your

specific ideas.

The integration of highly efficient solar cells into

portable consumer electronics, such as cell pho-

nes or hand held computers, offers a totally new

functionality, aiming for more independencefrom the electrical grid. In addition to the very

high-efficiency silicon solar cells used for our

SPISE (Solar Powered by ISE solar cells) techno-

logy, we offer professional electronic solutions as

well as space-saving and aesthetic device inte-

gration.

Another key field for the application of our PV

cells is their use in concentrator systems. Our

single-, tandem- or triple-junction concentrator

cells of silicon or compound semiconductors dis-play ultimate performance at the highest inter-

national level. Since cell efficiency is only one

requirement to create a successful concentrator

system, we have also focussed on the optical

and mechanical components of such systems

resulting in our unique FLATCON*design.

Applications for our photovoltaic cells are by no

means limited to solar energy conversion. For

example, GaSb low band-gap cells are used in

thermophotovoltaics to convert thermal radiati-

on with wavelengths up to 1750 nm into electri-city. Furthermore, these cells are excellent detec-

tors in the infrared. The list of useful applications

for our wide range of PV cells is long and still

growing.

The development of new photovoltaic cells at

Fraunhofer ISE is based on excellent technologi-

cal infrastructure and detailed understanding of

the physical background of photovoltaics. We

would be happy to share our experience with

you to let your specific idea become reality.

Our Offer

- product development and scientificsupport

- semiconductor components ready

for assembly

- feasibility studies on new technologies

Our Special Facilities

- clean-room laboratory for producing

high-efficiency silicon and compound

semiconductor solar cells

- epitaxial equipment for III-V semi-conductors (LPE: Liquid Phase Epitaxy

and MOVPE: Metal Organic Vapour

Phase Epitaxy)

- equipment for in-depth analysis of PV

cells and systems

Evaporation of metal contacts

* FLATCON: Fresnel Lens All-glass Tandem

Cell Concentrator


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Compound Semiconductor Technology

A highly flexible, industrial size MOVPE* reactor

is used for the process development and epitaxi-al growth of compound semiconductors. Fifteen

different sources are connected to this system,

which is used for the growth of arsenides, phos-

phides and antimonides for optoelectronic appli-

cations. In-situ measurement techniques allow

instant access to important growth parameters.

Six years of experience with this 8x4-inch multi-

wafer MOVPE* reactor give us a solid base for

understanding the many parameters involved.

Silicon Cells

Starting from a high level of cell efficiency, our

research has two main goals: the development

of new and innovative cell structures for a wide

range of applications like space or concentrating

systems and the transfer of high-efficiency cell

structures to industrial mass production. The

second goal in particular is achieved by a close

cooperation between the clean room technology

and our state-of-the-art industrial solar cell

production line.

Characterisation

The analysis of all optical and electrical losses is

one of several key points for the successful deve-

lopment of new solar cell structures. Our pool of

material and cell analysis tools is probably the

most comprehensive worldwide and can thus

cope with all challenges raised by the in-house

cell development. Certainly, it can also clarify

problems identified by our customers.

Solar Cell Technology

Fraunhofer ISE 3

AIX 2600-G3 MOVPE*

reactor with 8 x 4 or

24 x 2 configuration

Short-circuit current map of

a solar cell indicating the

spacial variation in material

quality on a silicon wafer.

Robot in the automatic photoresist

system for silicon wafers in the

clean room at Fraunhofer ISE.

* MOVPE: Metal Organic Vapour

Phase EpitaxyThe development of highly efficient

and customer-oriented solar cells has

a long and successful tradition atFraunhofer ISE. Our 500 m2 clean

room with its high-tech equipment

offers an optimal work bench for the

fabrication of both, silicon and com-

pound semiconductor solar cells.

With the aid of our comprehensive

characterisation tools for analysing

starting materials and cells, we have

achieved several international record

efficiencies.


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SPISETechnology

Fraunhofer ISE 4

SPISE* Solar Cell Technology

At the heart of SPISE* are high-efficiency silicon solar cells which deli-

ver significantly more power than

conventional cells. This difference is

even more pronounced at low illumi-

nation intensities. This is decisive for

power supplies for portable electronic

devices which are mostly operated

indoors.

SPISE* Module TechnologyFraunhofer ISE cells are interconnec-

ted in an innovative manner resulting

in increased module efficiency and

aesthetic appearance. Thanks to their

special design, it is possible to shingle

our cells and thus significantly reduce

the reflection due to the front metal

contacts. The modules are integrated

in the device housing, resulting in a

very elegant appearance.

SPISE* Electronics

Optimised system technology is vital

for a reliable power supply. Based on

our comprehensive experience in ultra

low power designs, we develop cus-

tom-tailored power conditioning units

like MPP-trackers, battery charging

circuits, battery management systems

and DC/DC-converters with ultra high

efficiency.

Increasing mobility, demanding grid-independent power supply, stimulates

the development of modern electro-

nic devices. An obvious solution is our

SPISE* technology which offers a

customised power supply for mobile

phones, hand-held computers, etc.

Fraunhofer ISE High-Efficiency CellCommercial Monocrystalline CellCommercial Multicrystalline Cell

* Solar Powered by ISE solar cells

100

Illumination Density / mW cm-2

4

8

20

24% Efficiency

12

0,01 0,1 1 10

16


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Concentrator Cells

Depending on the illumination density of theintended application, silicon concentrator cells

are used up to 100 suns whereas multijunction

cells made of compound semiconductors are uti-

lised at high concentration of up to 2000 suns.

Our unique high-performance technology is used

for silicon concentrator cells with efficiencies

reaching 25% at 30 suns. Stacking solar cells of

different compound semiconductor materials

allows us to increase the efficiency further.

Record values up to 32% have been obtained at

300-500 suns. A large variety of monolithic and

mechanically stacked concepts is available forconcentrator systems working between 10 and

2000 suns.

Specific Applications

Concentrator Systems

Recently we have developed the so-called

FLATCON* system using our own highest effi-

ciency monolithic multijunction solar cells. The

sun is concentrated by a factor of 500 by using

high quality Fresnel-lenses from silicone a ma-terial used in space module production. A short

focal distance of only 75 mm allows a compact

and flat design, hermetically sealed with glass.

An unparalleled performance of up to 25%

system efficiency has been reached. The entire

concentrator technology from the solar cell to

the tracking system, carrying up to 5 kW of

FLATCON modules has been developed in-

house. The concept is ready for market

introduction.

For latest news see also

www.pv-concentrator.com

Fraunhofer ISE 5

III-V concentrator cell 2mm

FLATCON* test modules

Special-Purpose PV Cells

A growing number of applications for low and

high band-gap cells of compound semiconduc-

tors can be found in thermophotovoltaics (TPV),

and for laser power and signal beaming.

- TPV systems convert the thermal radiation ofan emitter at 1000 1500 C, e.g. a gas burner,

directly into electricity. Applications are expected

in the low power range up to 500 W.

- For laser power transmission, high band-gap

semiconductors are used to convert the laser

beam into electricity. Useful applications are

found in the fields of telecommunications, signal

and energy transfer to rotating systems, and po-

wer supplies for switches and electronic devices.

A variety of different cell sizes, structures and

packaging has been realised.

From left to right: Cells and system for thermophotovoltaics

(left) and laser power transmission (right)

* FLATCON: Fresnel Lens All-glass Tandem

Cell Concentrator


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Address

Fraunhofer Institute forSolar Energy Systems ISE

Heidenhofstr. 2

79110 Freiburg

Germany

Tel.: +49 (0) 7 61/45 88-0

Fax.: +49 (0) 7 61/45 88-90 00

www.ise.fhg.de

Contact Persons

Silicon

Dr. Stefan GlunzTel.: +49 (0) 7 61/45 88 51 91

Fax.: +49 (0) 7 61/45 88 92 50

E-mail: [email protected]

Compound semiconductors

Dr. Andreas Bett

Tel.: +49 (0) 7 61/45 88 52 57

Fax.: +49 (0) 7 61/45 88 92 50


www.III-V.de

MOVPE

Dr. Frank Dimroth

Tel.: +49 (0) 7 61/45 88 52 58

Tel.: +49 (0) 7 61/45 88 92 50


www.epiproducts.de

System components: Electronics

Dr. Bruno Burger

Tel.: +49 (0) 7 61/45 88 52 37

Fax.: +49 (0) 7 61/45 88 92 37

E-mail : [email protected]

Module Integration

Dipl. Phys. Helge Schmidhuber

Tel.: +49 (0) 7 61/45 88 51 93

Fax.: +49 (0) 7 61/45 88 93 20

E-mail : [email protected]

www.pv-devices.com

Top: Diffusion furnace forsilicon solar cells.

Middle: FLATCONmodule.Bottom: Hand-held com-

puter powered by SPISE.

New premises for Fraunhofer ISE, planned anddesigned according to the motto: exemplarybuilding with the sun.

Visit us on the Internet!www.ise.fhg.de

Documents

Customised PV Cells