Transcript Dye-Sensitized Solar Cells

Agenda
• Do Now
• Dye-Sensitized Solar Cells Background
• Dye-Sensitized Solar Cells Lab Procedure
Lesson Objectives
• SWBAT explain how a dye-sensitized solar cell works.
• SWBAT describe the differences between conventional solar cells and
dye-sensitized solar cells.
Do Now
• Why is solar energy an important area of research?
• What are some of the problems facing current solar technology?
1
Available solar energy compared to global
consumption
2
3
Standard solar cell
• Composed of two different
semiconductors joined together
• When sunlight hits the cell, it
excites the electrons allowing
them to move throughout the
cell, creating a current
4
Problems faced by standard solar cells
• Expensive to produce
• Low efficiency
• Rigid
• Fragile
If you replaced our
current energy sources
with all solar energy, the
cost of electricity would
be 3 to 6 times higher
than current costs.
5
A brief history of dye-sensitized solar cells
• First developed in 1991
• Michael Grätzel was the
principal scientist working
on the project – DSSCs are
often called Grätzel cells
• Continues to be a huge area
of research as scientists try
to improve all aspects of the
cell and find new
applications for the
technology
6
Dye-sensitized solar
cell
• Sunlight enters through the
negative electrode (anode)
• A layer of dye-coated TiO2
nanoparticles sits between the
anode and the cathode
• The TiO2 allows the electrons
to travel through the cell
7
Dye-sensitized solar
cell
• The dye absorbs the photons
from the sunlight
• The photons excite electrons in
the dye, allowing them to
travel
• The electrolyte (usually iodide)
helps transfer electrons
• The cathode is typically
composed of graphite or
platinum
8
Advantages of dye-sensitized solar cells
• Cheaper
• Flexible
• Lighter
9
Disadvantages of dye-sensitized solar cells
• Efficiency is still low
• Many use liquid electrolytes
• Temperature stability
• Can be toxic if released into
the environment
• Some materials used are still
expensive
• Metals in the dyes
• Compounds in the electrolyte
• Short lifespan
10
Current DSSC Research - Electrolyte
• Cobalt based
electrolyte
• Iodine is typically used
in the electrolyte; it is
expensive and can
degrade quickly
11
Current DSSC Research - Dyes
• Zinc based dyes
• Zinc is cheaper and less
toxic than many of the
metals currently
employed
12
Current DSSC Research - Dyes
Non-metal dyes
13
Current DSSC Research –
Improving electron flow
• Using viruses and carbon nanotubes
to create DSSCs
• Carbon nanotubes allow electrons
to flow fast
• Virus helps create a defined
structure
14
Making your own dye-sensitized solar cell!
Materials
• 1 transparent indium tin oxide (ITO)-coated glass slide (referred to as ITO
slide)
• 1 TiO2-coated indium tin oxide glass slide (referred to as TiO2 slide)
• Iodide electrolyte solution (0.5 M potassium iodide mixed with 0.05 M
iodine in propylene glycol)
• 2 small binder clips
• 1 blackberry
• 1 spatula
• 1 pencil
• 1 piece of parafilm, cut into 20 mm x 40 mm size
• 1 small aluminum pan
• 1 paper towel
• 1 razor blade/scalpel/X-acto knife
• Multimeter
15
Crush the blackberry
• Place the blackberry in the aluminum pan.
• Using a spatula, crush the blackberry to extract the juices. Scoop out
the solid pulp
Note: you will be using the juices and you want have as little pulp in
the juice as possible
16
Coated slides
• There are two different types of coated slides!!!!
• TiO2
• ITO
• TiO2
• Determine which side the TiO2 coating is on.
• Place the glass slide with the TiO2 face down into the aluminum pan with the
blackberry juice. Allow to sit for 3-5 minutes. While it is soaking prepare the
ITO slide.
• After soaking gently dab it dry, DO NOT WIPE as you may remove some of the
TiO2
• ITO
• Determine which side the coating is on by using a multimeter with its setting
placed on resistance (Ω). The indium tin oxide coating is on the side of the
slide that gives a non-zero reading on the multimeter.
• Using the tip of a graphite pencil, lay down the carbon catalyst by shading the
indium tin oxide-coated side of the slide.
17
• Remove and discard the wax paper backing from the parafilm and
place the parafilm on top of the dye-coated TiO2 slide. Use the eraser
end of the pencil to press the parafilm to the glass slide in the area
that borders the TiO2.
• Using a razor blade, carefully cut out the area of the parafilm that sits
on top of the TiO2. Press lightly with the blade, so that the conductive
coating does not scratch off. Reinforce the parafilm seal around the
edges of the TiO2 area with the eraser end of the pencil.
18
• Place 1 drop of the iodide electrolyte solution on top of the TiO2. The
parafilm should act as a wall that prevents the electrolyte solution
from leaking out.
• Place the ITO-coated glass slide on top of the TiO2 slide so that the
conductive sides face each other. Stagger the slides so that as much
of the glass slide is exposed and the entire TiO2 is covered.
19
• Use the 2 small binder clips to hold the
slides together. Attach the clips on the
longer sides.
• Carefully push back a small amount of the
parafilm wall to expose a tiny part of the
conductive side of the slide.
• Place the multimeter probes on opposite
ends of the solar cell’s conductive glass
slides.
• Place the solar cell under light, using
either sunlight or a flashlight.
• With the multimeter set to measure
electric potential, measure the voltage of
the solar cell.
20
Visit:
http://community.nsee.us/concepts_apps/dssc/DSSC.html
Go through the presentation, play the game, and write 5 new
things you learned from this presentation that weren’t in
today’s presentation and 5 questions you have.
21