1. Juice from Juice Teaching Workshop
NSF Center for Chemical Innovation: Solar Fuels

2. Overview of JfJ Project
Goal: develop dye-sensitized solar cell (DSSC) kit that
Supports NGSS (3rd – 12th grade)
Gets students involved in solar-energy technology
Reinforces inquiry-based learning and invites further discussion/investigation from students
Integration of scientific concepts from multiple disciplines into one hands-on, engineering-based project
Physics
Chemistry
Biology
DSSC
Chemical potential
Electron transfer
Light
absorption
Engineering

3. Lesson Road Map Pre-lab Related Lessons Experiment Post-lab Next Steps
DSSC Background Information
Inquiry Opportunity: Renewable energy
Pre-lab
Water Splitting: Photosynthesis and Energy Storage
Light as Energy: Light reflection and absorption in gummy bears
Electrochemistry: Galvanic Cells, redox and the activity series
Related Lessons
DSSC Fabrication
Circuits: Connecting cells in series and parallel
Scientific Notation: Using a multimeter
Experiment
Calculating power and efficiency of a DSSC
Post-lab
Comparison to silicon solar cells and other dyes
Inquiry Opportunity: Fuel Cells
Next Steps

4. What is a Solar Cell? Traditional Photovoltaics vs. DSSCs
Sony Hana Akari (“flower light”) lamps: lampshades are screenprinted DSSCs
Caltech Holliston parking structure
Solar window prototype by Solaronix - EPFL
Traditional Photovoltaics
vs. DSSCs

5. DSSC Components Semiconductor Dyes used as photosensitizers
Chlorophyll (spinach leaves)
Anthocyanin (berries, fruits)
Betalin (beets)
Synthetic Ru dyes
Conductive glass electrodes
Redox electrolyte
Light source
TiO2
Blackberry Juice
FTO
Now Amanda will take you through the conceptual basics
I-/I3-
Projector or Sun

6. Juice from Juice DSSCs Dyed TiO2
Sandwiched layers with electrolyte in between
Completed DSSC
TiO2 layer
Graphite layer

7. How do the DSSCs work?
It all has to to with energy levels and band gaps
Light provides energy to excite an electron
As the electron moves down the energy levels, it can do work and generate electricity

8. Energy Levels of DSSCs
Image from Tan et. al., 1994

9. Energy Levels of DSSCs e-
c) Electrons collected from the TiO2 travel through the load to reach the counter electrode, where they are used to reduce triiodide
Light excites the dye, moving an electron to a higher energy
b) An electron from the dye is transferred to TiO2
d) Iodide is oxidized to release an electron back to the dye molecule.
HOMO
LUMO
TiO2 + CB VB
LOAD
I-/I3- e-
(a) Light excites an electron in the blackberry dye from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The dye in the excited state is denoted as DYE*. This excitation leaves behind a hole (h+).
Our load can be a light bulb or other electronic device.
Today it is a multimeter.
DYE+
DYE*
DYE

10. Energy Levels of DSSCs
Although we’ve spatially rearranged the energy levels, they still sit at the same energies!
HOMO
LUMO CB VB
LOAD
I-/I3-
Light excites an electron in the blackberry dye from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The dye in the excited state is denoted as DYE*. This excitation leaves behind a hole (h+).

11. Energy Levels of DSSCs e-
The electron ‘rolls’ down the potential hill, passing through the load, and returns to the ground state in the dye.
HOMO
LUMO CB VB e-
I-/I3-
LOAD
DYE
Light excites an electron in the blackberry dye from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO). The dye in the excited state is denoted as DYE*. This excitation leaves behind a hole (h+).
TiO2

12. Energy Levels of DSSCs
The sun does all the work for us! It throws the electrons to the ‘top of the hill,’ while we simply make use of the energy of the electron as it rolls down.
This is SOLAR ENERGY.
Why fto picture? What are the white circles? What are the black dots? Why depicted like this?

13. Chemical Reactions Resulting in Electron Transfer for Current Flow
Oxidation
3I-  I e-
Reduction
I3- + 2e-  3I-
2 e- + - -
LEO the lion goes GER
OIL RIG
Image credit:

14. Why this System? Materials are cheap, abundant, non-toxic
Right energy level alignment with all components (dyes, FTO, TiO2, I-/I3-, etc.)
Detectable current (I) and voltage (V)
Other options?
other fruits or synthetic dyes can be used as can other metal oxides besides TiO2
However, energy level alignment and electron transfer rates must be satisfied

15. Side Lesson: Using Multimeters
DC = Direct Current
Variable
Units of Measurement
Context
Current
‘I’
Amps (A) = Coulomb/sec
Electron travel rate
Voltage
‘V’
Volts (V) = Joules/Coulomb
‘Push’ [or energy] per electron packet
Resistance
‘R’
Ohms (Ω)= Volts/Amps
Opposing force [like friction in mechanics]
Power
‘P’
Watts (W) = Joules/ sec = Volts*Amps
Energy transfer rate
P = I*V
Joule’s Law
V = IR
Ohm’s Law

16. Side Lesson: Building Circuits
How do we maximize current or voltage from our solar cells?
In series
maximum voltage
In parallel
maximum current
These symbols (resistors)
represent our DSSCs!

17. Side Lesson: Building Circuits
How do we maximize current or voltage from our solar cells?
In series
maximum voltage
In parallel
maximum current

18. Related Expt: Water-splitting
DSSCs
Water Splitting
Uses sunlight to generate clean, renewable electricity
Makes clean, renewable fuel from water
Combine: H2 generation using DSSCs

19. Related Expt: Light & Energy
Nature of light
White light can be made from individual colors
Wavelengths of light can be absorbed or reflected, giving rise to the colors we see
Different wavelengths have different colors and energies

20. Related Expt: Electrochemistry
Electrochemistry key to the success of a DSSC
Output voltage due to reduction/oxidation (redox) reactions
Different metals have different reduction potentials
Create activity series using Zn, Cu, Sn, and Mg
Galvanic cell
DSSC
E (V)
-0.5
0.0
0.5
1.0

21. DSSC Kit Juice from Juice kits distributed by Arbor Scientific
Includes all materials for the experiment with a class of 30
DSSC Fabrication…..$140
Refill of chemicals or extra glass for larger classes available in refill kit
Chemical Refill……...$39
Glass Refill… $15
Most materials can be reused for several years

22. Other experiment Kits
Still in process of developing kits/setting prices
Also distributed by Arbor Scientific with materials for a class of 30
Water-Splitting………..$79
Electrochemistry….….$50
Light & Energy Experiment just requires
red & green laser pointers ($10-20 online)
Gummy bears

23. “I need help!” I don’t have enough $ for the kit!
Kids in Need Foundation, DonorsChoose.org, local power company grants
Donations from parents, PTA, bake sales
Even aluminum cans!
I don’t remember how to do it!
Lesson plans and instructional videos online
We can do a demo at your school if you are in the LA area
questions –
I don’t have time in my curriculum!
Lesson fulfills NGSS standards, cross-cutting concepts in many areas
Incorporate as much as you can – some renewable energy education is better than none!

24. Conclusions and goals Thanks – and have fun!
Integrate basic science with push towards clean energy
Get students and teachers directed toward research in solar energy conversion
Feedback and continued project development
Physics
Chemistry
Biology
DSSC
Chemical potential
Electron transfer
Light
absorption
Engineering
Thanks – and have fun!
Questions: