Dye Solar Cells for RealThe Assembly Guide for Making Your Own Solar Cells

David Martineau
Revision 02.09.2010

Solaronix SA
Rue de l'Ouriette 129
CH-1170 Aubonne
Switzerland
T +41 21 821 22 80
F +41 21 821 22 89
info@solaronix.com
www.solaronix.com

Dye Solar Cells for Real | Contents

A Bit of Theory!

6

Anatomy of a Dye Solar Cell!...........................................6
The Photovoltaic Magic!..................................................7

Let's Go

Glass Preparation!

8

Identifying the Conductive Side!......................................8
Cutting out Conductive Glass Plates !..............................9
Cleaning Conductive Glass Plates!..................................9The Titania Electrode!

10

Preparing the Substrate for Deposition!.........................11
Getting the Paste Ready!..............................................11
Doctor-Blading the Titania Paste!..................................12
Sintering the Titania Layer!............................................13
Making Room for Contacts and Sealing!.......................14
Re-firing a Titania Electrode!..........................................14

Staining the Titania!

15

Staining With a Natural Dye!..........................................15
Staining With a Synthetic Dye!......................................17

The Platinum Electrode!

20

Brush-Painting the Platinum Precursor!.........................21
Doctor-Blading the Platinum Precursor!.........................21
Firing the Platinum Electrode!........................................23
Testing the Catalytic Activity!.........................................23

The Carbon Alternative!

24

With a Pencil!................................................................24
With a Candle!...............................................................25

Putting Electrodes Together!

26

Quick and Easy, the Sealed Cell Configuration!..............27
Preparing for the Sealed Cell Configuration!...................28
Sealing Without a Protection Foil!..................................30
Sealing With a Protection Foil!.......................................32

Filling With Electrolyte!

34

Filling an Open Cell".......................................................34
Filling a Sealed Cell"......................................................35
Sealing the Filling Holes !...............................................36
A Final Touch!................................................................37

Testing the Solar Cell!

38

Dye Solar Cells for Real | 3©2010 Solaronix
This work is made available under the terms of the Creative Commons
Attribution Non-Commercial Share Alike 3.0 license.
http://creativecommons.org/licenses/by-nc-sa/3.0/

Dye Solar Cells for Real | Foreword

ForewordThank you for reading our guide to Dye Solar Cell (DSC)
assembly. This tutorial was inspired by requests fromDye# Solar# Cell enthusiasts looking for a place to start.
Some of them were scientist starting to investigate thetechnology, while others were professors who wanted toteach the assembly in training courses. Should you be insuch a situation or not, we hope you will find this tutorial to
be useful, helping you to successfully make your own
Dye#Solar#Cells!
There are many ways of making a Dye# Solar# Cell, withmany combinations of materials and designs. For instance,some people may make cells open to the air, while others
may choose to deposit the titania on their own. Some may
prefer natural dyes instead of ruthenium dyes, and carbon
cathodes instead of platinum cathodes, to make inexpensive solar cells for school activities.
This document attempts to cover all possible situations.
Therefore, several methods described for obtaining thesame part of a solar cell. The cathode, for example, can bemade from platinum or carbon. In such a case, only one
method needs to be employed, depending on materials
and equipment available. Readers are thus invited to pickand choose the sections relevant to the type of assembly
they desire.
This guide was compiled from comments and suggestions
from our readers. Please feel free to send us your comments and suggestions, so that we can continue to improve this tutorial.
The operation of a Dye Solar Cell is magical. Fortunately,
making them requires no magic, just the right tools, materials, and techniques that we are happy to share with you
here.
Good luck making your own Dye Solar Cells, and have fun!
– Dr. David Martineau

Dye Solar Cells for Real | 5

A Bit of Theory | Dye Solar Cells for RealA Bit of Theory
Let's have a quick review of the theory before getting our hands dirty. We won't spend too much timeon the underlying science that drives this fantastic
device, but rather focus on its anatomy and its basic
operation principle.

Anatomy of a Dye Solar Cell
Understanding first how Dye Solar Cells are built is
an excellent way to avoid many common mistakes
during the assembly. Learning from failure is completely optional, though frustrating.
A Dye Solar Cell is composed of two electrodes, theanode and the cathode. These electrodes are madefrom a specific glass that has a Transparent Conductive Oxide (TCO) coating on one side. The TCO
material is a thin layer of fluorine-doped tin oxide,
also called FTO. The transparency of the substrate
allows sunlight to enter the cell while its conductive
surface collects charges.

e-

The anode is the negative terminal of the solar cell. It
essentially bears a continuous network of sinteredtitanium dioxide nanoparticles. This porous network
offers an inner surface that is a thousand times
greater than the equivalent flat area, and acts like a“light sponge” in which sunlight can get trapped.
Titanium dioxide is a white semiconductor that is notsensitive to visible light. The titania particles have to
be sensitized with a layer of dye molecules absorbing light in the visible spectrum. Some natural dyes
can be employed, but the most efficient pigments
were synthesized after intense scientific investigation.
The positive terminal of the solar cell, also called thecathode, is coated with a catalytic material for electron transfer. In most cases, this catalyst is carbon or
platinum. Since a very small quantity of catalyst isneeded, the electrode remains transparent.

eDye

e-

e

e-

Ox.

e-

TiO2

Red.

Anode
(TCO Glass + Dyed Titania Particles)

6 | Dye Solar Cells for RealElectrolyte

Cathode(TCO Glass + Catalyst Layer)h!
DyeDye Solar Cells for Real | A Bit of Theory

The space left between the two electrodes is filledwith an electrolyte that ensures charge transportation through a redox couple. Iodide/tri-iodide in anitrile solvent is typically used for this purpose.
Eventually, the two electrodes are sealed together toprevent the electrolyte solvent from evaporating.
However, the assembly can remain open when simplicity is preferred over durability, such as during
training courses or short run tests.
We will see in this guide how to build the different
parts of a Dye Solar Cells in several configurations.

The Photovoltaic Magic
Now that you know what's under the hood, youprobably wonder how this device can produce electricity. We will reveal the magic trick of the photovoltaic effect happening in the solar cell.
Nature likes to keep opposite charges together sothat matter appears neutral. The photovoltaic effectis all about violating this rule. It creates a separationof charges in the solar cell under illumination. The
resulting pairs of electrons and “holes” will strive to
get together again, but we will only let them do soafter a short trip through an external circuit.
In a Dye Solar Cell, this charge separation happensat the interface of the titanium dioxide and the dye.
Remember that this interface is present all over theinternal surface of the porous layer. This allows the
Dye Solar Cell to form many, many separated
charges which produces an electric current, for agiven solar cell area. The structure of the Dye#Solar
Cell is one of the secrets of its efficacy.

The dye molecules have the ability to absorb visible
light. As they are excited by this phenomenon, themolecules will give up an electron and inject it into theadjacent titanium dioxide. The charge separation occurs when the electron is injected into the titania andthe “hole” is left behind on the dye molecule.
Not surprisingly, nature hates to have these charges
separated. The electron must return to the oxidized
dye molecule as soon as possible. That's were kinetics come into play: quick wins. The fastest routeback to the dye for the electron is to travel throughthe external circuit. It might be a longer distance totake the highway, but it's faster than a footpath.
Injected electrons migrate through the titanium dioxide particles and reach the TCO glass of the anode,
the negative terminal of the solar cell.
When a load is connected, electrons spontaneously
move to the positive terminal of the solar cell, thecathode, via the external circuit. This movement ofelectrons is what we call an electric current.
Thanks to the redox couple present in the electrolyte, electrons can finally be transported from thecathode's surface to the oxidized dye molecules.
Now that the charges are together again, new cycles
can be performed indefinitely as long as the sun
shines. This is how a Dye Solar Cell produces electricity by photovoltaic separation of charges.
That should be enough to quench your intellectual
thirst for the moment. Time to practice!

Dye Solar Cells for Real | 7

Glass Preparation | Dye Solar Cells for RealGlass Preparation

Parts: TCO Glass Plates
Different sorts of TCO glass plates are available
in standard sizes. Customized glass plates may
also be supplied upon request. The typicalsubstrates are the following.
- TCO30-8, (3#mm, 8#ohm/sq FTO)
- TCO22-7, (2.2#mm, 7#ohm/sq FTO)

This section focuses on the preparation of the glass substrates for those who would like to prepare their own electrodes from scratch. It includes cutting the glass to the desired size and gives advice for cleaning prior to making any
deposition.
The typical substrate for making Dye Solar Cells is a glass
plate coated on one side with a Transparent and Conductive Oxide (TCO) layer. The most frequently used conductive material for that purpose is fluorine-doped tin oxide(FTO). The terms TCO or FTO glass are often used to referto this kind of substrate.

Identifying the Conductive SideThe TCO glass plates are only conductive on one side.
Make sure to clearly identify the appropriate side while
making your cells. The deposition of materials discussed inthis tutorial will always be performed on the conductive side.
A multimeter set to measure resistance should typicallyread about 10# ohms when the two probe tips are placed
one millimeter apart in the middle of the plate. This value
may vary depending on the TCO glass type.
There's also an easy trick that requires no instrument. Thisis particularly handy for identifying which is the conductiveside at any time during the assembly. Scratch each side of
the glass with a plastic spatula or even your fingernail. The
conductive side is the one that feels a little sticky. The TCO
coating has a rougher surface than bare glass. Visually, thecoated side is also the one that looks hazy.

8 | Dye Solar Cells for Real

Dye Solar Cells for Real | Glass Preparation

Cutting out Conductive Glass Plates
Depending on the size of your raw glass plates and thesize of the solar cells you want to build, it may be necessary to cut the glass into smaller pieces. To achieve this,scribe a line on the TCO glass at the desired position using
a glass knife or a cutting table. We recommend you makethe scribe on the conductive side of the glass.
After the cutting line is scribed, immediately break the glassin two pieces by bending the plate from both sides of theline. Waiting too long will allow the glass to peel off along
the etch, making it much harder to break. Repeat this operation until you have the desired size of glass plates.

Cleaning Conductive Glass Plates

Attention: Glass Handling
Beware of cuts. The glass plates should be
handled with care since the edges of the glasscan be very sharp.

It is always a good idea to clean the TCO glass plates before any kind of deposition. Be sure not to use a roughscrubber that could scratch the conductive side, rather usea soft sponge dedicated to clean delicate cutlery or similar
things. The choice of the detergent is also of importance.
Soaps for dish washing aren't suited for cleaning TCO
glass, prefer the use of a specific glass detergents like
Deconex® from Borer Chemie. Such cleaning agents aredesigned to leave no residue when rinsed.
After cleaning, thoroughly rinse the glass plates with deionized water to prevent traces of minerals. Denatured alcohol
can also be used. Use a hot-air blower for faster drying.

Dye Solar Cells for Real | 9

The Titania Electrode | Dye Solar Cells for RealThe Titania ElectrodeThe titania electrode consists of a layer of titanium dioxide
nanoparticles on a TCO glass plate. Such a layer is obtained by the deposition of a paste containing a suspension of titania particles. Different formulations are available
and adapted to each deposition techniques.

Parts: Titania Pastes
The Ti-Nanoxide product line encompasses
titania pastes formulated for different
depositions techniques. Several sizes of titania
nanoparticles are available, including mixes
with large particles.

Parts: Ready to Use Titania Electrodes
We can provide titania electrodes ready to use.
They are prepared by screen-printing which
ensures homogenous deposition andcontrolled thickness.
- Spot Titania Electrode(for making high performance DSC).
- Education Titania Electrode(training courses and similar activities).
- Demonstration Titania Electrode(for making larger demonstration cells).

10 | Dye Solar Cells for RealThe titanium dioxide particles must be in the size range of
10-40# nm so that the resulting sintered layer is highly porous. This layer, at the center of the operation principle, will
ultimately act as a light-sponge in the solar cell. We use theterm nanoparticles when discussing particles in that size
range. Nanoparticles for the Dye Solar Cell are preferably
titania crystals of anatase phase, other crystalline structures can be detrimental.
The nanoparticles typically lead to a semi-transparent layer
after sintering. The resulting transparency of the electrode,
while offering design attractiveness, is not always desired.
A significant fraction of light is not collected but allowed topass through the solar cell, diminishing the conversion efficiency. This behavior can be circumvented with the use ofbigger titania particles.
Titania particles larger than 100# nm are big enough to interact with light and diffuse incoming beams. They are often used in the fabrication of opaque titania electrodes,
either mixed with the nanoparticles, or stacked in a diffusing layer. There are many types of titania pastes containing
either or both nanoparticles and big particles.
It is also possible to get pre-made titania electrodes. In thiscase, it is recommended to run a firing process before using them. This makes sure they don’t contain moisturefrom ambient air.

Dye Solar Cells for Real | The Titania Electrode

Preparing the Substrate for Deposition
The simplest and most widely used method for depositingtitania paste on a substrate is the so-called doctor-blade
method. The technique is also known as slot-coating in its
mechanized version. It uses a hard squeegee, or doctorblade, to spread a portion of titania paste onto the glass.
With this technique, the thickness of the titania layer is determined by the thickness of a spacer placed on bothsides. We recommend using the "Scotch Magic #810"
tape from 3M, which has a thickness of about 50 µm. This
tape can be easily removed from the glass without leaving
traces of glue.
With the conductive side facing up, apply two parallel stripsof tape on the edges of the glass plate, covering about 5 to
7 mm of glass. The area of uncovered glass in the middleof the glass is where the titania will be deposited. Edges
masked by the tape will give room for future sealing andelectrical contacts. Take advantage of the adhesive tape tohold the glass plate in position on the workbench. This will
prevent the plate from moving while making the deposition
stroke.

Attention: The Right SideThe TCO glass plates are only conductive on
one side. Make sure to clearly identify theappropriate side while making the assembly of
your cells. Deposition must be performed on
the conductive side.

Getting the Paste Ready
Settling of the titania paste can occur over time. Make sure
to start with a homogenous paste, stir well before use witha glass rod or similar tool. Don't shake the bottle, this cancreate air bubbles and prevent a good deposition.

Dye Solar Cells for Real | 11

The Titania Electrode | Dye Solar Cells for Real

Doctor-Blading the Titania Paste
Apply a portion of paste near the top edge of the TCO
glass between the two pieces of tape. With a rigid squeegee, such as a microscope slide or a glass rod, spread thepaste across the plate with the support of the adhesive
tapes on both sides. The gap between the strips of tapeshould be filled with a layer of titania paste. Repeat the operation until you have a reasonably homogenous layer.
This deposition technique can also be used to obtain aslightly thicker titania layer. This can be desirable for increasing the electrical output of the resulting solar cell. Following the same method, stacking two layers of adhesive
tape will make a thicker spacer for spreading the paste.
Please note however that having a thicker titania layer also
makes it more delicate to treat as it may crack during firing.
Start practicing with thin layers.
There are other deposition methods, such as spin-coating
and screen-printing which require the corresponding machinery and adapted titania paste formulations. This tutorial
will not discuss these topics, assuming the experimenter
willing to make titania electrodes with either of these advanced techniques is knowledgeable about the required
processes.

Parts: Doctor-Blade Titania Pastes
Formulations of anatase titania nanoparticles
are available for the doctor-blading technique.
The pastes are available in different particle
sizes, depending on the desired transparencyof the titania electrode.
- Ti-Nanoxide D, opaque electrode.
- Ti-Nanoxide T, transparent electrode.
- Ti-Nanoxide HT, highly transparent electrode.

12 | Dye Solar Cells for Real

Dye Solar Cells for Real | The Titania Electrode

Sintering the Titania Layer
The titania electrode is completed by firing the depositedlayer. The vehicle of the paste burns away, leaving the titania nanoparticles sintered together. This process ensureselectrical contact between particles and good adhesion to
the TCO glass substrate.
Sintering can occur in an oven, or on a programmable hotplate. First remove any adhesive tapes used for doctorblade deposition, and place the freshly coated glass platein or on the heating device at room temperature. Set thedesired temperature to 450°C. While heating up, you may
observe that the titania layer turns brown/yellow and releases fumes. This corresponds to the evaporation andcombustion of the non-toxic chemicals used in the paste
formulation. After 15 to 20 minutes at 450°C, the bakedtitania layer looks white again or transparent, indicating thatthe sintering process is over.
Allow the heating device to cool down before removing thefired electrode. A sudden change in temperature can cause
the glass to break. The resulting nanoporous layer madefrom the sintered particles can absorb moisture from ambient air, make sure to store the sintered electrodes in asealed environment soon after firing.

Attention: Glass BreakGlass plates are sensitive to sudden changes intemperature. Make sure to warm up and cool
down your samples at reasonable speed (50°C
per minute for instance). Rapid temperaturechanges can cause the plates to break.

Dye Solar Cells for Real | 13

The Titania Electrode | Dye Solar Cells for Real

Making Room for Contacts and Sealing
The sintered titania electrode has a band of titanium dioxide in the middle, with room for connection on two ends. It
might also be useful to make room on the two other edges
for laying a sealing gasket. Scratch away the excess ofmaterial on the other two ends with a non-metallic tool.
The titania area should then be confined to the middle of
the glass plate.
The electricity produced by the finished solar cell is collected from the edges of the glass electrodes. Therefore, itis necessary to have enough space for the electrical contacts, could they be clips or wires.

Attention: Non-Metallic Tool
Preferably use a non-metallic tool for scratchingtitania off the TCO glass. A metallic spatula canleave bits of metal that may eventually pollute
the solar cell.

Re-firing a Titania Electrode
Remember that titania electrodes might take up water andother pollutants from air when stored for a long period. It isbest to use the electrode right away.
If you are starting with an existing fired titania electrode, it isstrongly recommended that you re-fire the electrode. This
ensures that no pollutants are left on the titania surface
prior to solar cell assembly. Re-firing is done by simply repeating the firing procedure discussed above.

14 | Dye Solar Cells for Real

Dye Solar Cells for Real | Staining the Titania

Staining the Titania
Titanium dioxide is a white semiconductor that doesn’t
absorb visible light. Therefore, it is necessary to color, or
sensitize, the titania electrode with a dye that can absorb
as much light as possible in the visible light spectrum. Thissection discusses the different methods for staining a titania electrode with a sensitizing dye.

Staining With a Natural Dye
Green plants and their fruits are a fantastic source of natural dyes that absorb visible light. The red pigments found in
raspberries or blackberries can work especially well in Dye
Solar Cells. Red fruits are very handy for experimenting in
training courses where the use of synthetic dyes can be anissue.
The sensitization of titanium dioxide by natural dyes consists of soaking the titania electrode in mashed fruits.
Complete staining can take from several minutes to several
hours, while the dye molecules from the fruit juice naturally
adsorb onto the titania particles. The longer the electrodesoaks in the dye, the better dyed the titania will be.
Start crushing fresh red fruits in a petri dish or similar container. The fruits must be juicy enough to get the titania
electrode completely soaked.

Hint: Frozen Berries
Frozen berries are a good source of natural dye
and can be conveniently stored until the
moment of the experiments.

Dye Solar Cells for Real | 15

Staining the Titania | Dye Solar Cells for Real

Place the fired electrode onto the mashed fruits with thetitania surface facing down. If necessary, apply slight pressure on the glass plate so that the whole titania area issoaked by the mixture.
Close the container and wait for the staining to complete.
The sensitization process takes an hour or more. Wait aslong as possible, so that more dye molecules can attach to
the titania.

Remove the stained electrode and rinse it carefully withethanol. Wait a few minutes for the ethanol to evaporate or
use a hair-dryer to gently dry the electrode faster.

The resulting stained titania should now look red almost allover its surface. If not, put it back in the fruit juice for further dyeing.
Note that the mashed fruits don't offer a homogenous medium, and may cause a pattern on the stained titania
electrode. This is not a problem with the operation of thesolar cell.

16 | Dye Solar Cells for Real

Dye Solar Cells for Real | Staining the Titania

Staining With a Synthetic Dye
The staining procedure can also be realized by soaking thesintered titania electrode in a synthetic dye solution.
The dye molecules will naturally adsorb onto the titania
nanoparticles and won't be desorbed by rinsing. The synthetic dyes developed for the Dye Solar Cells contain anchoring groups that have a natural affinity for titanium dioxide surfaces.
Furthermore, these molecules are optimized for light collection and thus demonstrate better performances than natural dyes. We recommend using one of the most cited dyesin the scientific literature, typically the ruthenium sensitizer
Ruthenizer#535-bisTBA (also known as N719).

Preparing a dye solution:
First prepare a dye solution for the staining bath. Make surethe volume is adapted to completely immerse your titania
electrode.
A typical concentration is around 3#x#10-4#M in methanol or
ethanol. For instance, dissolve about 10# mg of dry dye
powder in 25# mL of methanol and stir until no traces ofsolid are visible. This might take up to several hours atroom temperature, depending on the concentration andsize of the powder granules. The solution usually becomes
deeply colored very quickly whereas only a small amount of
the dye has actually dissolved. Most of the solid takes
longer to dissolve but does not offer a drastic visualchange.
The staining solution can be prepared in advance and canbe used for several experiments. However, the dye solution
can be notably degraded by water and light. The dye getsoxidized and the solution changes in color. Keep the dyesolution away from light and moisture in a sealed bottle.
Preferably prepare small volumes each time and store drymaterial long term.

Attention: Dye HandlingDo not breath dust of dye and avoid ingesting
the sensitizer. Synthetic dyes aren’t fully tested
substances.

Parts: Synthetic Dyes
Here are some synthetic dyes demonstrating
very good sensitization of titania electrodes.
They offer an enjoyable color palette that helps
in making visually appealing solar cells.
- Ruthenizer 535-bisTBA, purple- Ruthenizer 620-1H3TBA, dark green- Sensidizer SQ2, vivid green

Dye Solar Cells for Real | 17

Staining the Titania | Dye Solar Cells for Real

Once your dye solution is ready, place the required amountof liquid in a staining bath vessel that can be kept tightly
closed.
Slowly immerse the sintered titania electrode in the staining
bath. The titania layer should be facing up, so that it doesn't
get scratched by friction on the bottom of the vessel.

Close the container and wait for the staining to complete.
The sensitization process typically takes 4 to 8 hours atroom temperature, depending on the titania layer thickness
and concentration of the dye solution. Staining can be accelerated by increasing the dye solution concentration if
necessary.
Several electrodes can be stained at a time in the same
vessel. The amount of dye present in the solution is muchgreater than what adsorb on the titania.
Remove the electrode from the bath and carefully rinse thestained titania with ethanol.

Attention: Away From Water and LightNo water should enter the sensitizing solution(air moisture is not critical). Keep the dyesolution away from light.

18 | Dye Solar Cells for Real

Dye Solar Cells for Real | Staining the Titania

While rinsing, it is recommended that you do not mix therinsing waste with the staining solution. The staining solution may be reused in future experiments.
The stained electrode can dry on its own, or you can use
a hair-dryer to evaporate the rinsing ethanol faster. The
freshly stained electrodes are meant to be used immediately, it is not advised to store them dry before assembly.
Better leave the electrode in the dye solution until it can beassembled.
Titania electrodes prepared during a previous session, orpurchased as is, can be re-fired so that the titania layer isfree of moisture or other contaminants that might have entered during storage.
If the titania electrode is prepared during the same session,
remove the electrode from the heating device when thetemperature is around 60°C and immerse it immediately inthe staining solution. This greatly reduces the chance theelectrode will adsorb any ambient moisture.

A properly sensitized electrode doesn't show any whitearea, especially when looking at the stained titania throughthe glass on the rear side.
For example, the absorbed dye should look deep red topurple whenever Ruthenizer 535-bisTBA is employed. If it
looks brown instead, the dye has been oxidized and won't
operate well in the solar cell.

Hint: Storing Dye Solutions
Store your dye solution away from light andmoisture to use it for other experiments. If you
are going to store the dye for a long time (i.e.
months or longer), evaporate the solvent anddry the solid dye completely before storingaway from light and moisture.

Dye Solar Cells for Real | 19

The Platinum Electrode | Dye Solar Cells for RealThe Platinum ElectrodeThe previous chapter described the making of anodes fromsintered titania particles. The Dye#Solar#Cell also requires acathode to complete the assembly.
The titania anode is where charge separation, the magic of
the photovoltaic effect, occurs. We often call the titania
anode the working-electrode. The cathode is frequently
referred as the counter-electrode.

Parts: Ready to Use Platinum Electrodes
We can provide you platinum electrodes readyto use. They are prepared by screen-printing
which ensures homogenous layer.
- Spot Titania Electrode(for the making of high performance DSC).
- Education Titania Electrode(training courses and similar activities).
- Demonstration Titania Electrode(for the making of larger demonstration cells).

This section and the following one details the fabrication ofplatinum and carbon counter-electrodes. Either one can beused as a cathode to make a Dye Solar Cell, however it is
not necessary to make both of them. The carbon electrodeis easier and cheaper to make, but we will focus first on theplatinum electrode which gives the best performance.
Platinum is known for its strong catalytic activity in electrontransfer at the counter-electrode. An efficient cathode for a
Dye Solar Cell can consist of a thin platinum layer on a
TCO substrate. This is obtained by the deposition of aplatinum precursor by either painting with a brush, doctorblading, or screen-printing. There are formulations of platinum precursors for these different deposition techniques.
It is also possible to get pre-made platinum electrodes. In
this case, it is strongly recommended to run a firing process at 450°C before using them in order to reactivate thecatalytic platinum layer. This process is detailed below.

20 | Dye Solar Cells for Real

Dye Solar Cells for Real | The Platinum Electrode

Brush-Painting the Platinum Precursor
Start with a TCO glass plate matching the size of the titania
electrode being used. Gently paint the platinum precursor
ink onto the conductive side of the TCO substrate with aregular brush. The catalytic layer of platinum will be active
after firing the painted TCO glass.
Firing should be completed soon after painting since theplatinum precursor can suffer from light exposure. Skip to
the firing section below to learn how to finish your platinum
electrode.

Attention: Light Sensitive Product
The platinum precursor paint is light-sensitive.
Make sure to store it away from light and fire
freshly painted electrodes rapidly.
Parts: Platinum Precursor Paint
Platisol T is a liquid solution of platinum
precursor that can be applied with a paintbrush.

Doctor-Blading the Platinum Precursor
The platinum precursor can also be applied by doctorblading from a viscous paste such as a formulation forscreen-printing. Start with a TCO glass plate matching thesize of the titania electrode being used.
This method is similar to the doctor-blading of titania paste
described earlier. With the conductive side facing up, apply
two parallel strips of adhesive tape on the edges of theglass plate, covering about 5 to 7# mm of glass. Take advantage of the adhesive tape to hold the glass plate in position on the workbench. This will prevent the plate frommoving while making the deposition movement.

Dye Solar Cells for Real | 21

The Platinum Electrode | Dye Solar Cells for Real

Apply a portion of platinum precursor paste near the topedge of the TCO glass between the two pieces of tape.

With a rigid squeegee, such as a microscope slide or a
glass rod, spread the paste down the plate with the support of the adhesives tape on either side.

Remove the adhesive tapes. The gap between the stripes oftape should be filled with a layer of platinum precursor paste.
The catalytic layer of platinum is obtained after firing. The
platinum precursor will turn into metallic platinum at elevated temperature. It is important to proceed with firing
quickly since the platinum precursor can degrade in light.

Attention: Light Sensitive Product
The platinum precursor paste is light-sensitive.
Make sure to store it away from light and fire
treated electrodes rapidly after deposition.
Parts: Platinum Precursor Paste
Platisol T/SP is a formulation of platinum
precursor for screen-printing that can be also
applied by doctor-blading.

22 | Dye Solar Cells for Real

Dye Solar Cells for Real | The Platinum ElectrodeFiring the Platinum Electrode
With either deposition technique, a firing process is necessary to activate the platinum layer.
Put the glass plate with freshly deposited platinum precursor in or on the heating device at room temperature. Set
the desired temperature to 450°C and maintain the electrode at this temperature for at least 10 minutes. The activated platinum layer forms during this time.
Allow the glass plate to cool down and remove it from theheating device. A sudden change in temperature cancause the glass to break.
This step can also be used to reactivate a platinum electrode
that was prepared in a previous session or purchased.
Platinum electrodes can be stored away from air and lightfor future use but will require re-firing prior to assembly.

Attention: Glass BreakGlass plates are sensitive to sudden changes intemperature. Make sure to warm up and cool
down your samples at reasonable speed (50°C
per minute for instance). A too rapid
temperature change can cause the plates tobreak.

Testing the Catalytic Activity
The resulting electrode features a nearly invisible layer ofplatinum. Its catalytic activity can be tested before continuing the assembly.
Place a drop of hydrogen peroxide on the electrode (a 30%
solution in water suffices). Bubbles should evolve from theplatinum surface within the drop, indicating the active platinum layer formed properly.
Clean with deionized water and ethanol to remove any traceof hydrogen peroxide prior usage of the platinum electrode.

Dye Solar Cells for Real | 23

The Carbon Alternative | Dye Solar Cells for RealThe Carbon Alternative

The cathode of a Dye Solar Cell is frequently made withplatinum, but carbon also demonstrates interesting catalytic activity. The carbon alternative, although being lessefficient than its platinum counter part, is easier andcheaper to realize. This makes carbon electrodes of greatinterest for educational purposes. Two practical ways ofmaking such a carbon counter-electrode are described here.

From a Pencil
Pencils can be a convenient source of carbon that’s very
easy to apply. Start with a TCO glass plate matching thesize of the titania electrode being used for the assembly.
Cover the entire conductive surface with the pencil. A discrete layer of carbon is now attached to the glass. It is notnecessary to have more material on the cathode. Your
electrode is ready to go, no need for firing.

24 | Dye Solar Cells for Real

Dye Solar Cells for Real | The Carbon Alternative

From a Candle
Another way to obtain a carbon electrode is through thedeposition of soot from a burning candle. Start with a TCO
glass plate matching the size of the titania electrode being
used for the assembly.
Light a candle and hold the piece of TCO glass, conductiveside facing down, about 10#cm above the flame. The carbon from the combustion of wax is carried in the smokeand makes a black deposition on the conductive side of
the TCO glass.
The process is very fast, so don't over do it. A homogeneous gray to black layer is enough.
Allow the glass plate to cool on a suitable surface before
further processing.

Attention: Hot Glass
During this procedure, the glass plate may
become hot and cause burns. Use a pair oftweezers for handling the glass safely.

Dye Solar Cells for Real | 25

Putting Electrodes Together | Dye Solar Cells for Real

Putting Electrodes Together
We have seen how to prepare a titania anode and acounter-electrode made from either platinum or carbon.
Now let's see how to assemble the two electrodes into asolar cell.
When the electrodes are put together, the active sides of
the anode and the cathode will be facing each other. In
other words, the stained titania will face the platinum or
carbon of the counter-electrode. The gap left between thetwo glass plates will be filled with electrolyte during thenext step.
This step can be accomplished using two different approaches. First, electrodes can be pressed together, andthe electrolyte soaked in the resulting stack by capillaryeffect. Second, the two electrodes can be sealed together
and the electrolyte injected via holes drilled through thecathode.
The first approach is called an “open cell” because the inner part of the solar cell is exposed to air. This is a very
easy setup, but the electrolyte won't be confined in the celland will eventually dry out. Such an assembly is practical
for training courses, where results must be obtained
quickly. However, the resulting solar cells won't last as longas in a sealed configuration.
The second approach is meant to give longer lasting solar
cells. The electrodes are sealed together with a gasket sothat the electrolyte is confined in the cavity. It certainly
takes more effort to manufacture, but it allows the Dye Solar Cells to operate for an undetermined period of time.
Depending on your goals, speed or durability, follow the
instructions for the open cell or sealed cell configurations.

26 | Dye Solar Cells for Real

Dye Solar Cells for Real | Putting Electrodes Together

Anodes and cathodes can be prepared either sequentiallyor simultaneously. Should one electrode wait for the preparation of the other, make sure to store it properly. For example, a stained titania electrode may be kept in the dyesolution until the counter-electrode is ready.

Quick and Easy, the Open Cell Configuration

Start with freshly made electrodes. The stained titania electrode should be used right after preparation. The cathodecan be fired again if it has been stored for several days ormore. Please refer to the sections about each electrode formore details.
Put the electrodes against each others so that the stained
titania is facing the platinum or carbon of the counterelectrode. The conductive sides of each electrode, face toface, forms the inside of the cell. Take care to slightly shift
the two glass plates in order to leave room for electricalcontacts.
Use paper binders or similar clips to hold the electrodes
together. Such a cell should be immediately filled with electrolyte before getting damaged by ambient air. Skip to theelectrolyte filling section to learn how.

Hint: Room for Contacts
It is very convenient to slightly shift the glass
plates to leave room for the contacts.

Dye Solar Cells for Real | 27

Putting Electrodes Together | Dye Solar Cells for RealPreparing for the Sealed Cell Configuration
In the sealed configuration, electrodes are put together
with the help of a hot-melt gasket around the titania area.
The cavity left by the sealing material between the two
glass plates ensures a confinement of the electrolyte in thesolar cell. With this approach, it is necessary to drill holes
through the cathode that will be used for filling the cell withelectrolyte during the next assembly step.
Drilling the cathode:
Drill two holes through the counter-electrode with a drill bit
appropriate for glass. Typical carbide drill bit diameters areeither 1.0 or 0.5 mm.
Position the two holes on opposite corners of the cell, andmake sure they fit in the inner dimensions of the gasket.
Electrolyte will be flushed from one end to the other.

Parts: Drilled Electrodes
Platinum electrodes can be ordered pre-drilled
for electrolyte filling.
- Drilled Spot Platinum Electrode(for the making of high performance DSC).
- Drilled Education Platinum Electrode(for the making of DSC in training courses).
- Drilled Demonstration Platinum Electrode(for the making of lager demonstration cells).

28 | Dye Solar Cells for RealFor a cleaner hole, drill half way through the glass fromboth sides. This will prevent the glass from chipping, which
can occur when the hole is drilled completely through fromone side.
Drilling the glass is a delicate step and you may prefer toperform so on a bare TCO glass before any deposition.
Beware that drilling too close to the edge of the glass cancause breakage.
TCO glass plates and platinum electrodes can be purchasedwith pre-drilled holes in order to avoid this difficult step.

Dye Solar Cells for Real | Putting Electrodes Together

Cutting out a gasket:
The sealed configuration requires cutting a gasket out of a
hot-melt film. This gasket will be used in the sealing procedures described below.
Cut out a rectangular sealing gasket from a sheet of hotmelt film with a knife. The inner dimensions should correspond to the area of the titania anode, the outer dimensions should be 3#mm bigger on all four sides.

Protected or non-protected sealing film?
Sealing films are available with an optional protection foil on
one side. Think about double-stick tape, they often comewith an additional plastic layer on the upper side. This allows you to conveniently apply the tape without it sticking
to your fingers. After removing the protection, the upperside of the tape becomes free for sticking.
The hot-melt film only sticks when heat is applied. The protection foil makes the process easier, completed in two
steps.
The next section will detail each of the possibilities. Selectthe one relevant to your sealing material.

Parts: Sealing Films
The hot melt sealing films can be used to cut
out gaskets. Different thicknesses are available,with an optional protection foil (“PF” option).
- Meltonix#1170-25 and Meltonix#1170-25PF- Meltonix#1170-60 and Meltonix#1170-60PF- Meltonix#1170-100 and Meltonix#1170-100PF

Dye Solar Cells for Real | 29

Putting Electrodes Together | Dye Solar Cells for Real

Sealing Without a Protection Foil
Start with freshly made electrodes. The stained titania electrode should be used right after preparation. The cathodecan be fired again if it has been stored for several days ormore. Please refer to the sections about each electrode formore details.
Carefully place the gasket around the titania area on theanode. The dimensions of the gasket and the stained titania shall match but not overlap. There should be one edgeof the electrode that's not completely covered by the gasket to leave room for electrical contacts.
With a soldering iron, and covering the gasket with a nonstick temperature resistant film such as a PTFE or PET foil,
melt a spot of material in each corner so that the gasket
slightly adheres to the glass. This optional step can help tohold the gasket in place prior to sealing.
Place the counter-electrode, conductive side facing down,
on top of the gasket. This stack keeps the sealing material
in place between the electrodes. If necessary, shift the two
glass plates in order to leave room for the the electricalconnections on both glass plates.

Parts: Pre-cut Gaskets
The gaskets in the dimensions for pre-madeelectrodes are available.
- Spot Gasket(for the making of high performance DSC).
- Education Gasket(for the making of DSC in training courses).
- Demonstration Gasket(for the making of lager demonstration cells).

30 | Dye Solar Cells for Real

Dye Solar Cells for Real | Putting Electrodes Together

Apply heat and pressure all over the gasket with the help of
a hot press or a similar tool set at about 110°C. After a few
tens of seconds, the hot melt material should glue the electrodes together. If not, repeat this operation until the wholesurface of the gasket has melted onto both electrodes.
A good adhesion of the sealing film to the glass plates canbe confirmed by a careful visual examination. The hot-meltmaterial should match the refractive index of the glass andlook completely transparent all over the gasket surface.
The degradation of finished Dye Solar Cells is almost always due to leaks from imperfect sealing. Temperature andpressure adjustments might be necessary to find the optimal conditions for your setup.
Remember that the stained titania electrode is sensitive to
air and light exposure. Even if the electrodes are now
sealed, air can still get in the cell because of the holes in
the cathode. Proceed directly to electrolyte filling.
Hint: From Protected to Non-Protected
The protective foil can be removed prior to use
in order to transform a protected sealing film
into its non-protected version. Put a piece ofadhesive tape on a corner of each side of thesealing film. Then pull away the two tapes apartso that the protective foil is detached from thesealing film.

Dye Solar Cells for Real | 31

Putting Electrodes Together | Dye Solar Cells for Real

Sealing With a Protection Foil
Sealing films can be purchased with a protection foil tofacilitate the sealing process. This protection consists of asecond plastic film sandwiched together with the sealingmaterial. The protection foil won't melt on the electrodes
and won't adhere to the sealing material or glass.
The whole sealing process can be done more comfortably
in two steps instead of one. First, melt the gasket onto one
electrode. Then peel off the protection with a pair of sharp
tweezers. Finally melt the other side of the gasket onto thesecond electrode. Find out how below.
Step 1:
Place the gasket on the conducting side of the cathode sothat it fits with the edges of the glass plate, with the protection foil facing up. There should be one edge of the electrode that's not covered by the gasket to leave room forelectrical contacts.
With the help of a soldering iron, melt a spot of material ineach corner so that the gasket slightly adheres to theglass. This optional step can help to hold the gasket inplace prior sealing.

Hint: Recognize the Protected Side
The protected side has a more glossy aspectand slides easier under one's fingernail.

32 | Dye Solar Cells for Real

Apply heat and pressure all over the gasket surface withthe help of a hot press or a similar tool set at 110°C. Afterfew seconds, the hot-melt material should have stuck to
the electrode. If necessary, put an additional PTFE or PET
film on top of the gasket to prevent accidental adhesion to
the hot surface. Repeat this operation until the whole surface of the gasket has melted onto the substrate.
Be careful not to apply too much pressure. This cancause the gasket to spread out, resulting in uneven gasket thickness.

Dye Solar Cells for Real | Putting Electrodes Together

Step 2:Thanks to the protection foil, the top side of the sealingmaterial didn't adhere to the hot press. Once cooled down,
peel off the protection foil with a knife or a pair of sharp
tweezers. The other side of the sealing material is now exposed and ready for a second sealing step. Just likedouble-stick tape.
Place the titania electrode, conductive side facing down,
on top of the gasket and align it with the area of stained
titania. The resulting stack of electrodes is ready for thesecond step of the sealing. The two glass plates should beslightly shifted to leave room for electrical connections.
Apply heat and pressure all over the gasket surface withthe help of a hot press or a similar tool set at 110°C. Afterfew a tens of seconds, the hot-melt material should glue
the electrodes together. If not, repeat this operation until
the whole surface of the gasket has melted onto both electrodes.
A good adhesion of the sealing film to the glass plates canbe confirmed by a careful visual examination. The hot-meltmaterial should match the refractive index of the glass andlook very transparent all over the gasket surface.
The degradation of finished Dye#Solar#Cell is almost always
due to leaks from imperfect sealing. Temperature and pressure adjustments might be necessary to find the optimal
conditions for your setup.
Remember that the stained titania electrode is sensitive to
air and light exposure. Even if the electrodes are now
sealed, air can still get in the cell because of the holes in
the cathode. Proceed directly to electrolyte filling.

Hint: Seal Holes for Delayed Filling
Use small pads of sealing film to temporarily
seal the filling holes. This protects the stained
titania from air and allows storage of theelectrodes in the dark. Once you are ready forfilling with electrolyte, simply peel off the pads
with a knife.

Dye Solar Cells for Real | 33

Filling With Electrolyte | Dye Solar Cells for Real

Filling With Electrolyte

The gap between the two electrodes can now be filled withelectrolyte to complete the Dye Solar Cell. This is performed either by capillary effect in open cells, or by injection through the filling holes in sealed cells.
It is best to fill the cells with electrolyte as soon as the electrodes are put together. The stained titania will otherwise
be exposed to air for too long and possibly degrade.

Filling an Open Cell
The electrodes have been put together and held with binders, immediately start filling with electrolyte before air andmoisture degrades the electrodes.
Place a few drops of electrolyte at the interface of the two
glass plates with a pipette, and allow the liquid to be drawn
into the cell by capillary effect. If necessary, repeat this operation until the entire internal surface of the solar cell iswetted with electrolyte.
Wipe off any excess liquid with a paper towel and manipulate the cell carefully to avoid skin contact with theelectrolyte.
The Dye Solar Cell is now operational and will last until theelectrolyte solvent evaporates.

Parts: Low Volatile Electrolyte
Open cells are most often prepared during
training courses, it is preferable to employ a
low volatile electrolyte in such conditions. We
have a formulation named Education
Electrolyte for that purpose.

34 | Dye Solar Cells for Real

Since the assembly is open to ambient air, the performanceof the cell will decrease over time. This assembly however
will give plenty of time to measure and demonstrate theelectrical output of the photovoltaic device.

Dye Solar Cells for Real | Filling With Electrolyte

Filling a Sealed Cell
The cavity formed by the sealing gasket between the two
sealed electrodes must be now filled with electrolyte. Beware that the holes drilled through the counter-electrodeexpose both electrodes to ambient air. Proceed directly toelectrolyte filling before the electrodes are damaged by air
and moisture.
Use a syringe to flush the electrolyte from one hole,through the cell, to the other hole. A small joint cut out of asilicon tube can be placed on the tip of the syringe to prevent leaks.
Complete filling can be confirmed by a visual examination.
A few small bubbles remaining in the solar cell are not detrimental to proper operation. Just make sure to get most of
the cavity filled.
Wipe off any excess electrolyte left around the filling holes
and clean the glass with an acetone wetted paper towel.
Any electrolyte left on the glass could hinder proper sealingof the filling holes in the next step.

Parts: High Performance Iodide Electrolytes
We recommended one of the following
electrolytes.
- Iodolyte AN-50, for best quick performance(50 mM iodide/tri-iodide in acetonitrile)- Iodolyte R-50, for long term stability(50 mM iodide/tri-iodide in methoxypropionitrile)

Dye Solar Cells for Real | 35

Filling With Electrolyte | Dye Solar Cells for Real

Sealing the Filling HolesThe two holes used for filling must now be closed to complete the sealed assembly. For this purpose, a small glasscap will be sealed on top of each hole with another pieceof sealing film.
It is very important that no electrolyte remains on or aroundthe filling holes. This will prevent adhesion of the sealingmaterial.
Repeat the operation described previously for sealing theelectrodes together, but with small glass caps and the corresponding pieces of sealing film.
Proceed in either one or two steps, depending on whether
the sealing film comes with a protective foil or not. Apply
heat and pressure on both seals with the help of a hot
press or a similar tool set at 110°C. After a few seconds,
the hot-melt material will seal the holes for good.
The resulting Dye Solar Cell is now ready for use. The
sealed configuration ensures the confinement of electrolyte
in the cell and prevents moisture from entering. A sealed
Dye# Solar# Cell can operate for an undetermined period oftime when assembled correctly.

Parts: Glass Caps and Sealing Pads
It is possible to get pre-cut glass caps andsealing pads. These tiny bits of materials cansave you a lot of time.

36 | Dye Solar Cells for Real

Dye Solar Cells for Real | Filling With Electrolyte

A Final Touch

Advanced experimenters may like to enhance current collection on the electrodes. Charge transport on the conductive glass is impaired by the resistivity of the FTO coating.
This effect can be reduced at the edges of the electrodes
by applying a more conductive material.
The space left for contacts on both electrodes can be
carefully painted with silver paint. The increased conductivity of this paint allows better flow of electricity generated in
the solar cell. Beware that the paint must not form a shortcircuit between the two electrodes.
Conductive adhesive tapes can also be placed on theglass edges to obtain the same enhancement. It is also
possible to solder a layer of tin on the TCO surface but thisrequires an ultrasonic soldering iron.

Dye Solar Cells for Real | 37

Testing the Solar Cell | Dye Solar Cells for Real

Testing the Solar Cell
Whether your cell is in the open or sealed configuration, it
is now ready for operation. If you are like us, your excitement for making solar cells is now at its zenith! Time to giveit a try!
Connect a voltmeter, negative end to the anode (titania
electrode) and positive end to the counter-electrode.
Measure the open circuit voltage under full sun illumination.
It should be around 0.6#V.
Note that the cell output can vary drastically upon the nature of the light source as they don't offer the same spectral quality. Prefer incandescent or halogen lamps to fluorescent bulbs.
Similarly, an ammeter allows for the measurement of theshort circuit current of the solar cell. This value can vary
greatly, depending on geometry of the cell and light conditions, as well as other internal parameters, such as titania
layer thickness and electrolyte composition. You may observe that your cells get better after a wear in period underillumination.
Parts: Electric Loads
Dye Solar Cells of a few square centimetersprovide enough current to spin a low current
motor. You might enjoy one of theseaccessories for your solar cells:- Low Current Motor.
- Model Wind Turbine.

38 | Dye Solar Cells for Real

Provided size and illumination are great enough, your cell
may be able to power a small electric load such as a low
current motor.

Get Involved
Dye Solar Cells for Real is published under the Creative
Commons Attribution Non-Commercial Share Alike license.
http://creativecommons.org/licenses/by-nc-sa/3.0/
We wanted this work to be open for people to use it as an
input for their own documents. You are therefore free tocopy, distribute, and adapt this work, under the following
conditions: You have to attribute Solaronix and the author,
and you must not use this work for commercial purposes.
If you modify or build upon this work, you need to shareyour work with the same license, so that the entire community can benefit from the derivatives.
We hope this guide will help you to make Dye#Solars#Cells.
Your feedback is greatly appreciated, feel free to send yourcomments and suggestions to David# Martineau(david.martineau@solaronix.com). We look forward to hearing from you.

Thank You
Special thanks to our Solaronix fellows who contributed to
the writing of this guide, Frédéric Oswald for the help inmaking pictures, and Michael Scott for his valuable input.
Thanks to all the readers whose comments helped in getting this document better.

Solaronix SA

Rue de l’Ouriette 129, CH-1170 Aubonne, Switzerland
info@solaronix.com" T +41 21 821 22 80
www.solaronix.com" F +41 21 821 22 89