64 renewable energy focus November/December 2009

Feature article

PV innovations on the leading edge for 2010 THERE ARE MANY MATERIALS, TECHNIQUES AND TECHNOLOGIES

READY TO ANNOUNCE THEIR ARRIVAL ON THE PV SCENE. ALL WILL

STRETCH THE PV FOCUS IN SOME WAY. SOME ARE VERY NEW AND

FARREACHING WHILE OTHERS ARE FOCUSED ON ADDRESSING

IMMEDIATE ISSUES. BUT ALL ARE READY TO BE IMPLEMENTED

WITHIN THE NEXT FEW MONTHS. JOYCE LAIRD ROUNDS UP THE

ONES TO WATCH.

AQT’s patented and

proprietary technology is

based on the production

of CIGS-type thin-film

photovoltaic cells using the

reactive sputtering process

(Courtesy of Applied

Quantum Technology)

renewable energy focus November/December 2009 65

PV/technology

The science behind innovation

There is no better place to start looking for

innovation than at the scientific level with

research that is not commercially vested in

promoting any single product or technology.

Argonne National Laboratory, Center for

Nanoscale Materials (Argonne, IL) is one such

centre. Argonne is a resource available to any

company which wants to take advantage of

leading edge technology.

Dr. Seth B. Darling, assistant scientist for

Argonne says that there are a number of

advances that look very promising in reducing

the cost of solar cells, including novel desensi-

tised solar cells using atomic layer deposition

(ALD). “ALD allows three dimensional struc-

tures to be very thinly conformally coated.

This reduces the distance that charges within

the device have to travel”.

Another is advanced luminescence concen-

trators. Conventional solar concentrators are

large devices that track the sun. “This type of

concentrator is stationary and it operates effi-

ciently under diffuse light, which is what you

need in low sun areas. We have developed

a model to optimise parameters associated

with this type of concentrator and we are

using that to direct the development of some

materials that are based on quantum dots.

These are nanocrystals of inorganic semicon-

ductor materials. It provides high lumines-

cence efficiency and the nature of quantum

dots allows tune-ability. You can tune their

band gap, or tune the amount of energy

they absorb. It also allows you to capture the

very broad light spectrum, even into the near

infrared part of the spectrum. There’s a lot of

the energy that other solar technologies are

not capturing,” he says.

“Argonne sits at the interface between the

long-term research academia and industry.

This is an important place to be. You need

that unbiased bridge between the two

worlds,” Darling says. “Ultimately of course, we

are not a company, so our goal is to hand off

our findings to a partner.”

Intermolecular, (San Jose, CA) is a different

type of research resource. It focuses on

combinatorial R&D i.e. performing multiple

levels of similar research simultaneously.

“Our equipment looks like a semiconductor

processing tool, but it is specifically built for

high volume R&D. You can process many exper-

iments very quickly in the same chamber in

parallel as opposed to doing them one at a time

using an entire solar substrate,” J. Craig Hunter,

vp and GM solar and energy technologies, says.

Whether crystalline or thin film, Hunter notes

that even minor changes in processing will

have an impact on the final product. Before

making the investment to move into full

production it is critical to understand exactly

what your process windows are and exactly

what the tolerances are for each of the indi-

vidual process parameters.

“We offer a very IP secure way of doing that on

a one-on-one basis with our customers,” Hunter

says. “We can process a thousand unique solar

cells per week, each with a different variation

on critical things that affect the performance

of that device. We also have software and

metrology systems that quickly and fully char-

acterise all solar cells and store it so the data

can be accurately compared and analysed.”

Helping support innovation

Components, equipment and materials also

fall into innovations that help PV manufac-

turers enhance both products and processes.

Components

BioSolar (Santa Clarita, CA) is on a mission

to replace components used within photo-

voltaic modules with something “greener”.

This may sound like an oxymoron, but in

truth, while solar is helping us move toward

a renewable energy source, many PV compo-

nent are not necessarily green. For example,

the main material in backsheets is typically

petroleum. BioSolar’s alternative is called

the BioBacksheet.

“There are several different types of back-

sheets, but all are petroleum based. 90

percent of crystalline and certain amorphous

silicon thin film use one type. More modern

thin films, CIGS and Cadmium telluride also

use a backsheet but they have more strin-

gent requirements. They need an absolute

moisture barrier,” David Lee, ceo says.

BioBacksheet uses a proprietary formulation

based on cotton and a form of nylon resin

made from castor bean oil. Lee says that it

provides a perfect moisture barrier environ-

ment as well electric insulation.

The company is just gearing up to go into

limited production. Samples will be available

for all PV manufacturers to test by early 2010.

Equipment

Tyco Thermal Controls based in Menlo Park,

CA came to the TFPV via semiconductors and

then through flat screen TVs. “We had the

big flat heaters that are needed to heat the

flat screens and it was just a step to taking

End of Abound Solar manufacturing line, including final packaging (Courtesy of Abound Solar)

66 renewable energy focus November/December 2009

PV/technology

that up to the large-scale heating needed for

thin film vacuum deposition and for final thin

film lamination. One type of heater provides

radiant heat for vacuum deposition and the

other conductive heat for the lamination

process.” Chris Mayes, director of product

marketing says.

“We make a very even heating substrate.

Then we put a cable into the back. We allow

for the edge effect where edges can get

cooler and we put more cable into them.

We’ve gone from a typical two foot by two

foot to a six foot by six foot rough average.

That, plus the change from the traditional

heated oil media to the heated coil, makes

the process more stable and requires much

less maintenance,” Mayes says. “We see

ourselves as an enabling technology,”

Materials

Heraeus Photovoltaic business unit was orig-

inally part of the Thick Film Division of WC

Heraeus, the precious metals and technology

group, headquartered in Hanau Germany. This

past January it spun off into its own busi-

ness unit and is growing fast with divisions

in Germany, China, the USA and one soon to

open in Taiwan.

The unit has developed a new front-side silver

paste that offers higher efficiencies along with

superior contact quality and aspect ratios on

both mono and multi-crystalline wafers and a

wide range of sheet resistance emitters.

“The chemistry of our latest SOL9235H

cadmium-free silver metallization paste

enhances the etching of the anti-reflective

coating and significantly improves the contact

quality of the cell,” Andy London, Heraeus PV

business unit manager says.

According to London, it gives c-Si PV manu-

facturers efficiency values that are between

0.3% and 0.5% higher than other products.

“We intend to produce two to three new

products per year. If we can help people

improve efficiencies and get better output,

that is our goal,” London says.

Integral Technologies (IT), Inc. (Bellingham,

WA) has a technology that is more on the

brink currently; a pellet created from a propri-

etary blend of conductive polymers.

Development actually began when the

company was contracted to come up with

a flat panel antenna system for satellite

tracking, which also needed a plastic bottom

side that could carry an electric charge. No

major company had such a material available.

“Conducting our own experiments, we came

up with a mixture that worked,” Bill Robinson,

ceo says. “We developed a pellet that could

be injection molded into a three dimensional

shape or be extruded. It was also ideal for the

bottom plate of a solar panel.”

Robinson says that the material is right for

both c-Si an TFPV. In the thin film area when

two plates of glass are used, this can effec-

tively replace the bottom plate. For crystal-

line silicon, he sees the material replacing the

aluminum used to put solar panels together.

“ElectriPlast has efficiencies similar to current

materials, but is far less expensive,” he says.

The company currently has the capacity to

manufacture up to 50,000 lbs of material a

month. Robinson says that they will soon be

targeting PV, and want to get involved and

work with customers hands-on.

Another company working on a new tech-

nology that will be rolling out early next

year is Plextronics Inc. (Pittsburgh, PA). Their

offering to the PV world is also a conductive

polymer technology but in the form of an ink.

Plexcore OC ink, is a multi-functional, custom-

isable, conductive material compatible with a

wide range of printing techniques. It creates

an absorption layer of only about 200 nano-

metres. Plextronics refers to it as 3rd genera-

tion thin film.

“Conductive polymers go into the terawatt

capacity,” James Dietz, vp of business devel-

opment says. “The technology is still in the

development stage, but we make demos

here. We buy substrates, glass or plastic, then

ElectriPlast is equally conductive but far less expensive to use than other solar materials (Courtesy of Integral Technologies, Inc)

Featured companies ■ ABB Inc.

http://www.abb.com

■ Abound Solar

http://www.abound.com

■ Applied Materials

http://www.appliedmaterials.com

■ Applied Quantum Technology

http://www.appqtek.com

■ Argonne National Laboratory

http://www.anl.gov

■ Ascent Solar Technologies Inc.

http://www.ascentsolar.com

■ BioSolar

http://www.biosolar.com

■ Heraeus

http://www.heraeus-thickfilm.com

■ Integral Technologies, Inc.

http://www.itkg.net

■ Intermolecular

http://www.intermolecular.com

■ Odersun AG

http://www.odersun.de

■ Plextronics, Inc.

http://www.plextronics.com

■ SANYO Energy (USA) Corporation

A Division of SANYO North

America Corporation

http://www.sanyo.com/solar

■ Shrink Nanotechnologies, Inc.

http://www.shrinknano.com

■ Tyco Thermal Controls

http://www.tycothermal.com

■ XsunX Solar

http://www.XsunX.com

renewable energy focus November/December 2009 67

PV/technology

we print our active or photovoltaic layer onto

this and finish it to a completed module. It’s

quite simple and that is the appeal.”

“We have over 20 customers now for our ink

and it is a diverse base. One is for indoor

applications because the product shows

a very high efficiency under fluorescent

lighting. Another is for a solar panel manu-

facturer. We only launched the initial product

late last year and we are already seeing a lot

of potential.”

c-Si, TFPV and beyond

All innovation culminates in actual produc-

tion. As manufacturers move steadily toward

cell improvement, they draw on both in-house

and outside expertise.

Abound Solar (Loveland, CO) creates thin

film solar cells based on cadmium telluride

(CdTe) technology. According to Dennis

Csehi, vp of engineering, this technology

greatly streamlines manufacturing and holds

down cost while delivering competitive

cell power.

“It’s a very simple process. It is all done in a

vacuum. The semiconductor layer is all done

in one shot. From there we do our backend

processing which is laser scribing followed by

module assembly. Unlike others in the thin

film market our assembly is not a lamination

process. We have a proprietary process that

we use for putting the backplate and the

active plate together,” Csehi says.

The company is currently producing products

and field testing arrays. They recently passed

certification of their process.

“We recently announced two customers in

Germany; Juwi and Wirsol. They have long

term agreements to buy our products and use

them in large scale installations,” Csehi says.

Michael Bartholomeusz, ceo of Applied

Quantum Technology (AQT), headquartered

in Santa Clara, CA says that AQT’s mission

is to achieve the highest cost/performance

ratio of any solar cell manufacturer. “Our

patented, proprietary technology is based on

the production of CIGS-type thin-film photo-

voltaic cells using the reactive sputtering

process. Sputtering is the proven standard

for producing other high volume cost sensi-

tive products such as hard and optical discs.

This approach includes single-step deposition,

nano-engineering, device-enhancing source

materials, and simplified cell interconnect

design,” Bartholomeusz says.

AQT intends to focus on cost reduction and

performance enhancement via nano-engi-

neering. The company is are embarking on

pilot production (15MW) and has a customer,

LOI (for a 2MW installation) in place.

Another TFPV player that is getting ready to

roll out in volume is Ascent Solar Technolo-

gies Inc. Look for this to happen in January,

2010 from the company’s new 30MW head-

quarters in Thornton, CO.

Ascent Solar uses CIGS thin-film technology

but on a clear plastic substrate. Also, its cells

are both extremely lightweight and flex-

ible. The manufacturing process is done at

the module level using roll-to-roll, mono-

lithic integration. The only way to produce a

product at a module level is through mono-

lithic integration, and monolithic integration

needs to use a transparent insulator. Light has

to go through it.

The process uses thermal co-evaporation

to deposit the four metals; copper, indium,

gallium and selenium onto the moving poly-

vinyl, plastic substrate. This forms the ideal

CIGS compound in the ideal thickness.

“Producing at the modular level means we don’t

have any external wiring. Everything is done inter-

nally just as in integrated circuit (IC) processing.

That enables us to go to large modules and high

voltage which is a big advantage,” Farhad Mogh-

adam, president and ceo says.

The flex-cells produced by this technology can

cut to order, from a module five meters long

to the size of a credit card. The uniqueness of

the product is that it remains flexible; not just

the PV module but even after encapsulation.

The modules achieve 11%+ efficiency.

“Our business model is focused on the BIPV,

(Building Integrated PV) and EIPV (Electronic

Integrated PV), not the utility market,” Mogh-

adam says. “Our flex cells need no special

framing or mounting. They can slip right into

fabricated pockets and can be glued directly

to metal or fabric surfaces.”

When talking about thin film, Odersun is

always on the leading edge of innovation. The

most unique aspect of the Odersun cells is

that they can be created in any size or dimen-

Odersun ells are produced by creation of a Copper-Indium-disulphide semiconductor on long reels of Copper Tape (CISCuT)

(Courtesy of Odersun AG)

68 renewable energy focus November/December 2009

PV/technology

sion, as proven with the trapezoidal modules

used to form concentric rings that powered

the visitor centre buildings of the Olympic

Park in Beijing in 2008.

Odersun has grown considerably since its

pilot plant created the Beijing solution. It is

now ramping up to full production, targeting

both the BIPV and the custom consumer

roofing markets.

“In Germany, many people have custom roofing

designed. Because of this, roofing architects

are seeking companies who can provide solar

modules that can fit unique designs,” Dr. Hein

Van der Zeeuw, ceo, says.

This flexibility of Odersun solar modules

comes from the basic manufacturing

methods. Cells are produced by creation of

a Copper-Indium-disulphide semiconductor

on long reels of Copper Tape (CISCuT). Being

just 1 cm wide and 0.1 mm thick this copper

tape is not only used to form the CIS semi-

conductor but also acts as the substrate

and the carrier material for the solar cell.

Using this patented “reel-to-reel” production

process, the 0.001 mm thin active cell layer is

created in only 3 stages.

Completed reels of solar cells are then cut

into strips, slightly overlapped and inter-

connected using conductive glue to form

SuperCells. The length of the individual cell

strips determines the current that can be

drawn, and the number of cells intercon-

nected in series defines the voltage. The

modules are composed of one or multiple

SuperCells connected in parallel. They can

be individually packaged in either a flexible

film laminate or a rigid glass-film laminate.

In this way the size, power and design of the

modules can always be adjusted to suit each

customer’s exact specifications.

In 2009 Odersun’s efforts went into building a

30MW factory. Its next commercial project

is for a railway station in Germany which

will start construction in the first quarter

of 2010. And there are three more 30MW

factories on the horizon for Odersun. These

will be strategically placed globally for best

market penetration.

Moving to crystalline (c-Si) technology, even

with the relative maturity of this market, there

is still a lot of ground-breaking going on. Much

of it is in the area of developing better and

leaner processes.

Applied Materials, Santa Clara, CA is at

the forefront in this area. “As the world’s

largest supplier of crystalline silicon (c-Si)

production equipment, our systems are

used in manufacturing the world’s most

efficient commercially available solar cells,”

Ken MacWilliams, vp of technology and new

products for Applied’s crystalline silicon solar

business, says.

One example is Applied Material’s project

with Baccini Cell Systems (Baccini Esatto).

Combining Baccini’s products and technolo-

gies with Applied’s expertise in processing

technology, automation and R&D resources,

results in world-class factory production tools

for advanced c-Si solar cells.

The first of several applications of this

collaboration is for double-printed metal

line deposition. This has been shown to

raise absolute cell efficiency by as much

as 0.5%. “These systems’ high productivity,

advanced ultra-thin wafer handling and

extensive automation can drive significant

cost reductions, resulting in lower cost per

Watt,” MacWilliams says.

“Today, approximately 80% of PV solar panels

produced are based on c-Si technology because

it has shown excellent long-term reliability and

performance over several decades of use. The

cost of US$1/Watt will be demonstrated in a

few years. Applied Materials will continuing to

offer new and continuous improvement prod-

ucts (CIP) to fulfill current and next generation

needs,” MacWilliams says.

Not all innovations are c-Si or TFPV. What

about the best of both worlds? That’s how

Sanyo (Tokyo, Japan) thinks. Its HIT (Hetero-

junction with Intrinsic Thin-layer) solar cell is

an original technology. This hybrid combines

a crystalline silicon substrate and amor-

phous silicon thin film. To date, it offers the

world’s best power generation level per unit

of installation area, based on superior high

energy conversion efficiency and tempera-

ture resistance.

“With crystalline silicon-type PV cells, the most

important issue for reducing the cost of PV

systems is the achievement of both energy

conversion efficiency and a thin silicon wafer,

which is the energy generation layer,” Robert

Zerner, business development executive, Solar

Division says.

Sanyo’s most recent breakthrough HIT cell

improvement was realised recently using a

cell thickness of 98 micrometers, which is less

than half previous cell thickness. This comes

with a 22.8% cell energy conversion efficiency,

which has been independently verified by

the National Institute of Advanced Industrial

Science and Technology.

While still confined to R&D and installation

tests. Zerner says that this has a very prom-

ising future. “The key for Sanyo is achieving,

We don’t do anything unless we can do it with

100% accuracy,” he adds.

Future Tech

Some innovations are well past the drawing

board stage, but not quite ready to roll into

full production. These are some that should be

making the news within the coming year.

Shrink Nanotechnologies, Inc., Carlsbad, Cali-

fornia produces a shrinkable plastic film. “One

for this film is building PV solar cells, but not

the type that are normally envisioned. Our

technology involves solar concentrators,” Mark

Baum, ceo says.

Ms. Sayantani Ghosh, PhD, assistant professor

of Physics at UC Merced and consultant to

Shrink Nanotechnologies explains that this

technology is a completely unique process.

“In a solar cell you take sunlight, and convert it

into electricity,” she says. “What we are doing is

Sanyo’s HIT solar cell is a hybrid model that combines a

crystalline silicon substrate and an amorphous silicon

thin film (Courtesy of Sanyo Energy (USA) Corporation)

renewable energy focus November/December 2009 69

PV/technology

taking sunlight and converting it into light of

a diff erent colour. This diff erent coloured light

then falls onto existing silicon PV. The colour of

the light is set to the PV’s preferred colour. It is

like straining the sunlight into colours that will

enhance the effi ciency of the silicon.”

“Think about a window. Instead of glass,

the surface of the pane would be a very

thin solar concentrator between two layers

of glass. The light of day will hit that solar

concentrator. By using crystalline silicon

around the edges of the pane, that silicon

would absorb the photons coming off the

quantum dots in the film. This would be

absorbed into the system and ultimately be

turned into electricity that could be used.

This same technology can apply to home

siding and roof shingles. It’s all about func-

tionalising the surfaces of the buildings that

people live and work in,” Baum says.

XsunX, Solar (Golden, CO), develops TFPV

solar cell technologies and manufacturing

processes. Intevac, Inc. provides magnetic

media deposition equipment to the HDD

industry. Put the two together in a joint busi-

ness agreement and out comes a new level

of equipment for manufacturing of CIGS

thin-film solar cells.

“We came up with a way to integrate our

thermal evaporation with their sputtering to

create a new process that combined the best

of both: high efficiency of thermal evapora-

tion and the high throughput of sputtering,”

Tom Djokovich, XsunX ceo says.

These systems take a 5” to 8” square thin fi lm

and process it the same as it would a hard

media disk. The HDD technology lays down the

back contact and then the evaporation system

deposits the CIGS layer. Then subsequent proc-

esses lead to the fi nal application of the front

contact layer. The systems are targeted to

produce 600 to 1,000 cells per hour.

“Laboratories are working with small struc-

tures to test out CIGS PV cell samples;

4” x 4” or 6” x 6” to come up with new effi-

ciencies. However, when scaling up to large

format cells, it introduces variables. You have

changed from what worked in the labora-

tory to something completely different. You

look at CIGS and the contrast between what

has been achieved in laboratories and what

is seen in real production is almost 100%

reduction in efficiency,” Djokovich says.

“The reality is that if you have something

that technically works in a small structure,

the goal should not be making it larger but

to simply make it small but at a very high

throughput – say 1,000 per hour. That’s what

we will do,” he adds.

Bringing it home

ABB is well known for automation and robots,

but it also has a solar division that is dedicated

to providing turnkey solar plants. While not a

pure PV innovation, this is defi nitely where

most of the innovations fi nd a home.

“We produce everything that goes into that

plant with the exception of the panels and

the trackers,” Rick L Ulam, business develop-

ment manager says. “Even on the trackers

though, we put in the automation and the

motors,” he adds.

Based on the GPS location, ABB calculates the

irradiance for that site and then designs and

builds the optimum plant for the customer.

It can do this because ABB is not tied to any

one type of solar technology.

The unique integral automation system is able

to turn inverters on earlier in the morning and

shut them off later at night. Doing this over

20 years produces a lot more power. Even if

a storm rolls in and panels are pulled in to a

fl at position the plant will still produce power.

The automation system senses that and pulls

in additional panels to compensate.

“We focus on the reliability of the plant from

all aspects. Say an inverter goes down, it

rearms automatically. Our automation system

will sense what is going on in the plant and

if it is not a fault condition will rearm itself. It

is basically a ‘Smart Plant’,” Ulam says.

ABB currently has 9 projects in progress for

concentrating solar power (CSP) and there

are 6 for PV. “CSP is thermal power genera-

tion where a mirror trough works in the

plant and focuses on a point. That heats up

a working fluid. Then that working fluid goes

through a heat exchanger and creates steam.

That steam drives the turbines that generate

the power. So we are involved in both CSP

and straight PV,” Ulam explains. “ Right now

the markets are dynamic and developers are

hooking up with companies that can help

them. That’s what we can do,” he adds.

Ending thoughts

Looking at the wide range of technologies

that are either already in the field or that will

be rolling out by mid 2010, it’s easy to see

that nothing is yet a truly definitive leader.

It is an exciting time to be in the solar

market and what we will be talking about

by this time next year, may just be a gleam

in the eye of an entrepreneurial PV engineer

or scientist today.

About the author:

Based in California, Joyce Laird has been writing for a

wide range of industrial magazines for over a decade.

Her extensive background in the semiconductor industry

created a perfect transition to covering developments in

photovoltaics.

Click through

Interested in further information on this

topic? Click on the following links from

the digital issue of the magazine:

PV manufacture: synergy without dependence – http://tinyurl.com/pckey7

Can the solar photovoltaic industry beat the economic downturn? – http://

tinyurl.com/pftuok

How to handle defective PV cells and wafers – http://tinyurl.com/ofsd3s

Solar PV Innovation: the new buzz – http://tinyurl.com/y9usf9x

XsunX systems take a 5” to 8” square thin film and process

it the same as it would when processing a hard media

disk (Courtesy of XsunX Solar)