Juice from Juice Workshop Presentation (Slightly condensed) Updated April 2015

Overview of JfJ Project Goal: develop dye-sensitized solar cell (DSSC) kit that 1.Supports state science curricula and standards (3 rd – 12 th grade) 2.Gets students involved in solar-energy technology 3.Reinforces inquiry-based learning and invites further discussion/investigation from students Integration of three scientific fields under one DSSC unit Physics ChemistryBiology DSSC Chemical potential Electron transfer Light absorption

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

Today’s Workshop anthocyanin TiO 2 surface on FTO glass hνhν e-e- “Sandwich” dye- sensitized solar cell photosensitizer photo = light

DSSC Components TiO 2 nanoparticle paste Natural dyes used as photosensitizers – Chlorophyll (spinach leaves) – Anthocyanin (berries, fruits) – Betalin (beets) Conductive glass electrodes (FTO) Redox electrolyte (I - /I 3 - ) Light source (projector or sun) John Muir HS Chemistry student (PUSD)TiO 2 electrode soaking in crushed berries

Assembling the Electrodes TiO 2 layer TiO 2 layer dyed with blackberry juice Assembled sandwich Completed cell with electrolyte in between the layers Graphite counter electrode

This ball has potential energy and can do work by knocking over some dominos at the bottom of the hill Conceptual DSSC Explanation The ball is like an electron – we can get the electrons to “roll down a hill” to make electricity!

Atomic Energy Levels Energy 1s 2s 2p First, consider General Chemistry’s atomic-orbital energy levels. Electrons populate these energy levels, and can be excited to higher energy levels. We use similar energy diagrams for electrons in molecules and solids, too!

Extension of Energy Levels to DSSCs 1s 2s 2p Energy

Extension of Energy Levels to DSSCs Energy TiO 2 Dye I - /I 3 - 1s 2s 2p Energy

Electron Transfer Energy TiO 2 I - /I 3 - But for our new energy diagram, there is no spatial x- axis dependence, so let’s rearrange the locations to see our analogy better. In this scheme, we positioned the energy levels to spatially correspond to our materials’ locations. Dye

Electron Transfer TiO 2 Dye I - /I 3 - Load We also added a load that the electrons pass through, as in the picture. Although we’ve spatially rearranged the energy levels, they still sit at the same energies! Energy

Electron Transfer TiO 2 Dye I - /I 3 - Load Light excites the electron in the dye from the dye’s valence band to its conduction band Energy

Electron Transfer TiO 2 Dye I - /I 3 - Load The electron then ‘rolls down the hill,’ passing through the load ‘knocking over dominos,’ then returns to the ground state in the dye Energy

Electron Transfer TiO 2 Dye I - /I 3 - Load The electron then ‘rolls down the hill,’ passing through the load ‘knocking over dominos,’ then returns to the ground state in the dye Energy

Electron Transfer TiO 2 Dye I - /I 3 - Load The electron then ‘rolls down the hill,’ passing through the load ‘knocking over dominos,’ then returns to the ground state in the dye Energy

Electron Transfer Energy TiO 2 Dye I - /I 3 - Load 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 electrons’ energy as it rolls down! This is our SOLAR ENERGY.

Electron Transfer Energy TiO 2 Dye I - /I 3 - Load Our load can be a light bulb or other electronic device. Today it is a multimeter.

Chemical Reactions Resulting in Electron Transfer for Current Flow Image credit: w/bp/ch19/oxred_2.php Reduction I e -  3I - w Oxidation 3I -  I e e LEO the lion goes GER OIL RIG

Using Multimeters DC = Direct Current VariableUnits of MeasurementContext 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/AmpsOpposing 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

Why this System? Materials cheap, abundant, non-toxic Right energy level alignment of dyes, FTO, TiO 2, I - /I 3 -, graphite Detectable I and V Other dyes [other fruits or synthetic dyes] can be used, other metal oxides besides TiO 2 can be used; however, energy level alignment and electron transfer rates must be satisfied

Sub-Module: Biology Plants Solar Cells Light AbsorberMoleculesMaterials Fuel ProducedChemicalElectrical Fuel StorageYesNo Chlorophyll and colored markers contain various pigments (chemical compounds) that have different affinities for solid vs. liquid phase Separate via thin layer chromatography (TLC) Characterize by R f value Effect of color of light on absorption TLC plate

Sub-Module: Chemistry Output voltage due to reduction/oxidation (redox) reactions – Different metals have different reduction potentials – Create activity series using Zn, Cu, Sn, and Mg E (V) Galvanic cell DSSC

Sub-Module: Physics Nature of light – White light can be made from individual colors (additive) – Prisms disperse white light into its components – Dark colors absorb some light and transmit/reflect others (subtractive) Converting light to electricity: solar cells – Conversion efficiency – Output dependence on intensity and color

Commercial DSSC Kits Juice from Juice kits distributed by Arbor Scientific Includes all materials for the integrated labs we have developed – DSSC Fabrication………………..$110 – Electrochemistry (Chem) & Chromatography (Bio).……….$50 – Light & Solar Cells (Phys) ……$70 – DSSC Refill.………………………...$39 – Chem Refill.……………………..…$19 Enough materials for a 30 person class Materials can be reused for several years

“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!” – YouTube videos and lesson plans online – We can do a demo at your school! – questions – “I don’t have time in my curriculum!” – All the labs fulfill state standards! – Incorporate as much as you can – some renewable energy education is better than none

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