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You may have noticed
that I'm wearing two different shoes.

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It probably looks funny --

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it definitely feels funny --

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but I wanted to make a point.

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Let's say my left shoe corresponds
to a sustainable footprint,

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meaning we humans consume
less natural resources

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than our planet can regenerate,

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and emit less carbon dioxide
than our forests and oceans can reabsorb.

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That's a stable and healthy condition.

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Today's situation
is more like my other shoe.

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It's way oversized.

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At the second of August in 2017,

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we had already consumed all resources
our planet can regenerate this year.

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This is like spending all your money
until the 18th of a month

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and then needing a credit
from the bank for the rest of the time.

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For sure, you can do this
for some months in a row,

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but if you don't change your behavior,

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sooner or later,
you will run into big problems.

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We all know the devastating effects
of this excessive exploitation:

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global warming,

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rising of the sea levels,

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melting of the glaciers and polar ice,

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increasingly extreme
climate patterns and more.

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The enormity of this problem
really frustrates me.

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What frustrates me even more
is that there are solutions to this,

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but we keep doing things
like we always did.

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Today I want to share with you

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how a new solar technology can contribute
to a sustainable future of buildings.

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Buildings consume about 40 percent
of our total energy demand,

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so tackling this consumption

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would significantly reduce
our climate emissions.

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A building designed
along sustainable principles

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can produce all the power
it needs by itself.

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To achieve this,

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you first have to reduce
the consumption as much as possible,

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by using well-insulated walls
or windows, for instance.

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These technologies
are commercially available.

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Then you need energy
for warm water and heating.

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You can get this
in a renewable way from the sun

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through solar-thermal installations

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or from the ground and air,
with heat pumps.

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All of these technologies are available.

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Then you are left
with the need for electricity.

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In principle, there are several ways
to get renewable electricity,

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but how many buildings do you know
which have a windmill on the roof

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or a water power plant in the garden?

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Probably not so many, because usually,
it doesn't make sense.

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But the sun provides abundant energy
to our roofs and facades.

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The potential to harvest this energy
at our buildings' surfaces is enormous.

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Let's take Europe as an example.

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If you would utilize all areas
which have a nice orientation to the sun

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and they're not overly shaded,

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the power generated by photovoltaics

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would correspond to about 30 percent
of our total energy demand.

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But today's photovoltaics
have some issues.

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They do offer a good
cost-performance ratio,

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but they aren't really flexible
in terms of their design,

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and this makes aesthetics a challenge.

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People often imagine pictures like this

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when thinking about
solar cells on buildings.

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This may work for solar farms,

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but when you think of buildings,
of streets, of architecture,

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aesthetics does matter.

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This is the reason why we don't see
many solar cells on buildings today.

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They just don't match.

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Our team is working on a totally
different solar-cell technology,

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which is called
organic photovoltaics or OPV.

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The term organic describes

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that the material used
for light absorption and charge transport

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are mainly based on the element carbon,

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and not on metals.

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We utilize the mixture of a polymer

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which is set up by different
repeating units,

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like the pearls in a pearl chain,

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and a small molecule
which has the shape of a football

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and is called fullerene.

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These two compounds are mixed
and dissolved to become an ink.

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And like ink,

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they can be printed with simple
printing techniques like slot-die coating

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in a continuous roll-to-roll process
on flexible substrates.

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The resulting thin layer
is the active layer,

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absorbing the energy of the sun.

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This active layer is extremely effective.

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You only need a layer thickness
of 0.2 micrometers

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to absorb the energy of the sun.

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This is 100 times thinner
than a human hair.

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To give you another example,

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take one kilogram of the basic polymer

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and use it to formulate the active ink.

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With this amount of ink,

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you can print a solar cell
the size of a complete football field.

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So OPV is extremely material efficient,

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which I think is a crucial thing
when talking about sustainability.

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After the printing process,

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you can have a solar module
which could look like this ...

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It looks a bit like a plastic foil

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and actually has many of its features.

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It's lightweight ...

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it's bendable ...

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and it's semi-transparent.

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But it can harvest the energy
of the sun outdoors

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and also of this indoor light,

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as you can see with this small,
illuminated LED.

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You can use it in its plastic form

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and take advantage of its low weight
and its bendability.

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The first is important when thinking
about buildings in warmer regions.

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Here, the roofs are not designed
to bear additionally heavy loads.

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They aren't designed
for snow in winter, for instance,

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so heavy silicon solar cells
cannot be used for light harvesting,

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but these lightweight solar foils
are very well suited.

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The bendability is important

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if you want to combine the solar cell
with membrane architecture.

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Imagine the sails
of the Sydney Opera as power plants.

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Alternatively, you can
combine the solar foils

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with conventional construction
materials like glass.

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Many glass facade elements
contain a foil anyway,

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to create laminated safety glass.

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It's not a big deal to add
a second foil in the production process,

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but then the facade element
contains the solar cell

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and can produce electricity.

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Besides looking nice,

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these integrated solar cells come along
with two more important benefits.

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Do you remember the solar cell
attached to a roof I showed before?

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In this case, we install the roof first,

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and as a second layer, the solar cell.

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This is adding on the installation costs.

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In the case of integrated solar cells,

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at the site of construction,
only one element is installed,

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being at the same time
the envelope of the building

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and the solar cell.

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Besides saving on the installation costs,

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this also saves resources,

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because the two functions
are combined into one element.

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Earlier, I've talked about optics.

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I really like this solar panel --

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maybe you have different taste
or different design needs ...

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No problem.

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With the printing process,

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the solar cell can change
its shape and design very easily.

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This will give the flexibility
to architects,

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to planners and building owners,

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to integrate this electricity-producing
technology as they wish.

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I want to stress that this is not
just happening in the labs.

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It will take several more years
to get to mass adoption,

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but we are at the edge
of commercialization,

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meaning there are several companies
out there with production lines.

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They are scaling up their capacities,

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and so are we, with the inks.

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(Shoe drops)

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This smaller footprint
is much more comfortable.

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(Laughter)

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It is the right size, the right scale.

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We have to come back to the right scale
when it comes to energy consumption.

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And making buildings carbon-neutral
is an important part here.

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In Europe,

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we have the goal to decarbonize
our building stock [by] 2050.

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I hope organic photovoltaics
will be a big part of this.

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Here are a couple of examples.

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This is the first commercial installation
of fully printed organic solar cells.

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"Commercial" means that the solar cells
were printed on industrial equipment.

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The so-called "solar trees"
were part of the German pavilion

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at the World Expo in Milan in 2015.

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They provided shading during the day

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and electricity
for the lighting in the evening.

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You may wonder why this hexagonal shape
was chosen for the solar cells.

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Easy answer:

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the architects wanted to have
a specific shading pattern on the floor

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and asked for it,

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and then it was printed as requested.

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Being far from a real product,

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this free-form installation hooked
the imagination of the visiting architects

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much more than we expected.

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This other application
is closer to the projects

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and applications we are targeting.

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In an office building
in São Paulo, Brazil,

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semitransparent OPV panels
are integrated into the glass facade,

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serving different needs.

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First, they provided shading
for the meeting rooms behind.

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Second, the logo of the company
is displayed in an innovative way.

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And of course, electricity is produced,

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reducing the energy footprint
of the building.

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This is pointing towards a future

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where buildings are no longer
energy consumers,

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but energy providers.

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I want to see solar cells
seamlessly integrated

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into our building shells

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to be both resource-efficient
and a pleasure to look at.

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For roofs, silicon solar cells
will often continue to be a good solution.

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But to exploit the potential
of all facades and other areas,

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such as semitransparent areas,

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curved surfaces and shadings,

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I believe organic photovoltaics
can offer a significant contribution,

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and they can be made in any form
architects and planners will want them to.

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Thank you.

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(Applause)