Teaching Workshop NSF Center for Chemical Innovation Solar Fuels Overview of JfJ Project Goal develop dyesensitized solar cell DSSC kit that Supports NGSS 3 rd 12 th grade Gets students involved in solarenergy technology ID: 487013
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Slide1
Juice from Juice Teaching Workshop
NSF Center for Chemical Innovation: Solar FuelsSlide2
Overview of JfJ Project
Goal: develop dye-sensitized solar cell (DSSC) kit thatSupports 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
EngineeringSlide3
Lesson Road Map
Water Splitting
: Photosynthesis and Energy Storage
Light as Energy
: Light reflection and absorption in gummy bears
Electrochemistry
: Galvanic Cells, redox and the activity series
Scientific Notation
: Using a
multimeter
Circuits
: Connecting cells in series and parallel
Comparison to silicon solar cells and other dyes
Calculating power and efficiency of a DSSC
DSSC Fabrication
DSSC Background Information
Inquiry Opportunity
: Renewable energy
Inquiry Opportunity
: Fuel Cells
Pre-lab
Experiment
Post-lab
Next Steps
Related LessonsSlide4
What is a Solar Cell?
Traditional
Photovoltaics
Caltech Holliston parking structure
Sony Hana
Akari
(“flower light”) lamps: lampshades are
screenprinted DSSCs
Solar window prototype by Solaronix - EPFLvs. DSSCsSlide5
DSSC Components
SemiconductorDyes used as photosensitizersChlorophyll (spinach leaves)Anthocyanin (berries, fruits)Betalin (beets)Synthetic Ru dyes
Conductive glass electrodes
Redox electrolyte
Light source
TiO
2
Blackberry Juice
FTO
I
-/I3-P
rojector or SunSlide6
Juice from Juice DSSCs
TiO
2
layer
Dyed
TiO
2
Graphite
layer
Sandwiched layers with electrolyte in between
Completed DSSCSlide7
How do the DSSCs work?It all has to to with energy levels and band gaps
Light provides energy to excite an electronAs the electron moves down the energy levels, it can do work and generate electricitySlide8
Energy Levels of DSSCs
Image from Tan et. al., 1994Slide9
Energy Levels of DSSCs
e-
HOMO
LUMO
DYE
DYE*
Light
excites the dye, moving an electron to a higher
energy
TiO
2
+
CB
V
B
LOAD
I
-
/I
3
-
Our load can be a light bulb or other electronic device.
Today it is a multimeter.
DYE
+
b) An
electron from the dye is transferred to
TiO
2
c) Electrons
collected from the TiO
2
travel through the load to reach the counter electrode, where they are used to reduce
triiodided) Iodide is oxidized to release an electron back to the dye molecule.Slide10
Energy Levels of DSSCs
HOMO
LUMO
CB
V
B
LOAD
I
-
/I
3
-
Although we’ve spatially
rearranged the energy levels, they still sit at the same energies!Slide11
Energy Levels of DSSCs
HOMO
LUMO
The electron
‘rolls’
down the
potential hill,
passing through the
load, and returns
to the ground state in the
dye.
CB
V
B
LOAD
I
-
/I3-e-
DYE
TiO
2Slide12
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.Slide13
Chemical Reactions Resulting in Electron
Transfer for Current Flow
Image
credit
: http://chemed.chem.purdue.edu/genchem
/topicreview/bp
/ch19/oxred_2.phpReduction I
3- + 2e
- 3I-
w
Oxidation
3I
- I3- +2e-
-
2 e
-
+-
LEO the lion goes GER
OIL RIGSlide14
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 TiO
2 However, energy level alignment and electron transfer rates must be satisfiedSlide15
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 LawSlide16
Side Lesson: Building Circuits
How do we maximize current or voltage from our solar cells?In seriesmaximum voltageIn parallel
maximum current
These symbols (resistors)
represent our DSSCs!Slide17
Side Lesson: Building Circuits
How do we maximize current or voltage from our solar cells?In seriesmaximum voltageIn parallel
maximum currentSlide18
Related Expt: Water-splitting
DSSCs
Water
Splitting
Uses
sunlight to generate clean, renewable electricity
Makes clean, renewable
fuel from water
Combine:
H
2
generation using DSSCsSlide19
Related Expt: Light & Energy
Nature of lightWhite light can be made from individual colors Wavelengths of light can be absorbed or reflected, giving rise to the colors we seeDifferent wavelengths have different colors and energiesSlide20
Related Expt: Electrochemistry
Electrochemistry key to the success of a DSSCOutput voltage due to reduction/oxidation (redox) reactionsDifferent metals have different reduction potentialsCreate activity series using Zn, Cu, Sn, and Mg
E
(V)
-0.5
0.0
0.5
1.0
Galvanic cell
DSSCSlide21
DSSC Kit
Juice from Juice kits distributed by Arbor Scientific
I
ncludes
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 kitChemical Refill……
...$39Glass Refill…............$15 Most materials can be reused for several yearsSlide22
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 bearsSlide23
“I need help!”
I don’t have enough $ for the kit!Kids in Need Foundation, DonorsChoose.org, local power company grantsDonations from parents, PTA, bake salesEven aluminum cans! I don’t remember how to do it!
L
esson plans and instructional videos online
http://thesolararmy.org/jfromj
We can do a demo at your school if you are in the LA area
Email questions – juicefromjuice@caltech.eduI don’t have time in my curriculum!Lesson fulfills NGSS standards, cross-cutting concepts in many areasIncorporate as much as you can –
some renewable energy education is better than none!Slide24
Conclusions and goals
Integrate basic science with push towards clean energyGet students and teachers directed toward research in solar energy conversionFeedback and continued project development
Thanks – and have
fun!
Questions:
JuiceFromJuice@caltech.edu
Physics
Chemistry
Biology
DSSC
Chemical potential
Electron transfer
Light
absorption
Engineering