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CNSI Nanoscience Lab Experiment Session October 1st, 2016

Nicholas De Marco, Taylor Aubry

Rita Blaik, Elaine Morita

Dye-‐SensiIzed Solar Cells What is a Solar Cell? Silicon Solar Panels are Expensive to Fabricate

Dye SensiIzed Solar Cells (DSSC)

•  Advantages –  Inexpensive

•  Disadvantages – Lower efficiency – Less stable

Overview of DSSCs

Components: 1.  Transparent conducIve

electrode 2.  Titanium dioxide (TiO2) 3.  Dye (Anthocyanin) 4.  Electrolyte (Iodine) 5.  Counter conducIve

electrode 3I I3 - -

Making a Dye SensiIzed Solar Cells

Conductive Substrate Catalyst

Electrolyte

Dye

Porous Matrix

Conductive Substrate

Stage 1

Stage 2 Top of Device

Bottom of Device

Building the Bottom Electrical Contact Step 1: Affixing Substrate to Table

Make sure that 4-5 mm* of this edge is covered in tape!

*Note: 1 mm is about the thickness of a ATM card or driver’s license

Conductive Side Down

4 – 5 mm Wide

Conductive Side Up

Scotch Tape

•  Do not let the glass pipe[e rotate or roll

•  Apply even downward pressure with each hand

•  When sweeping back to the taped edge, use a single stroke to cover the enIre slide

Apply Drops of TiO 2 Slurry

Glass Pipette

Glass Pipette Slide Pipette ONCE

1

3

2

Helpful Tips:

Building the Bottom Electrical Contact Step 2: Coating with Titania

Move back and forth vertically

Building the Bo[om Electrical Contact

TiO2 Coated Substrate

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CoaIng Challenge

•  Do not let the glass pipe[e rotate or roll

•  Apply even downward pressure with each hand

•  When sweeping back to the taped edge, use a single stroke to cover the enIre slide

Apply Drops of TiO 2 Slurry Move Back and Forth

Glass Pipette

Glass Pipette Slide Pipette

1

3

2

Helpful Tips:

The Transparent ConducIve Electrode Q1: Why is it important that the top conducIve electrode be transparent?

Why is it important that the top conducIve electrode is transparent?

What do you think of as an electrical conductor?

Why is it important that the top conducIve electrode is transparent? FTO: Fluorine doped tin oxide

A transparent conductor!

Bottom of Device

The Titanium Dioxide NanoparIcles Q2: Why is it important that the TiO2 are nanoparIcles?

Titania Nanopar'cles Serve as a Docking Site for the Dye

Journal of Photochemistry and Photobiology A: Chemistry 213, 2010 30

Ruthenium Dye Anthocyanin Dye

~$300/g Cheap!

Scanning Electron Microscope Image of TiO2 NanoparIcles

How Small is “Nano”? Why is it important that the TiO2 are nanoparIcles?

Hint: Le` and right images take up approximately the same area…

What’s different?

NanoparIcles have more surface area!

Why is it important that the TiO2 are nanoparIcles?

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Why is it important that the TiO2 are nanoparIcles?

More surface area means more dye molecules can adsorb to the TiO2 and more electrons (current) can be generated!

3I I3 - -

Anthocyanin Dye

Where Does Anthocyanin Come From? Anthocyanin: our dye sensiIzer comes from plants!

Anthocyanin responsible for purple pigment in food and plants!

Food Source Anthrocyanin Content (mg/100g)

Cherry 375

Raspberry 365

Blueberry 558

Black Raspberry 589

Purple corn 1642

An Anthocyanin Fourth of July Cake!

Anthocyanin: our dye sensiIzer comes from plants!

The Anthocyanin Dye Q3: How can dye selecIon affect solar cell performance?

Anthocyanin appears purple/red, at what wavelength does it absorb light?

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Colorful dyes absorb sunlight (that’s why they are colored) and generate electrons that can be collected by electrodes to provide an electrical current

We can pick dyes that absorb anywhere! So what goes into our choice?

Wavelength 750 nm 400 nm Energy 1.65 eV 3.1 eV

Inte

nsity

Different wavelengths of light have different energy!

Higher energy Lower energy

What if my dye absorbed blue light instead of green light?


Inte

nsity

Ene

rgy

ΔE = 3.1eVΔE = 2.2eV

Each electron would absorb more energy!

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So why don’t we make all our solar cells absorb blue light?

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1) The sun produces light over a large spectrum! 2) Need to balance current and voltage to opImize power

What if I increase the intensity of light?


Inte

nsity

Ene

rgy

Would each electron would absorb more energy?

ΔE = 3.1eV

What if I increase the intensity of light?


Inte

nsity

Ene

rgy

No! But more electrons can be excited and thus

ΔE = 3.1eVmore current can be generated!

Which light has more energy? (per photon)


Inte

nsity

Current vs. voltage analogy

Suppose 4 people are at the bo[om of a cliff…


If the cliff is very high, they might not all make it up

Current vs. voltage analogy But when they jump down, they have super strength!


If the cliff is very low, they all have enough energy to jump up!


When they jump down they have a lower strength score, but there was more of them!

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The Iodine Electrolyte Q4: Why does the Iodine need to be there anyway?

Let’s break down the redox reacIon

3I − → I3−

→ [I − I − I ]−I −

I −I −

e-‐ e-‐ e-‐

e-‐

Energy Level Diagram of our DSSC

Anthocyanin Dye Iodide Solution

Titanium Dioxide

E

Energy GeneraIon Step 1: Excite


Titanium Dioxide

E Incident Light

PotenIal Pathway: Energy Loss


Titanium Dioxide

E Emitted Light

Energy GeneraIon Part 2: Transfer


Titanium Dioxide

E (Needs to be FAST!)

Energy GeneraIon Part 3: Replenish


Titanium Dioxide

E (Needs to be FAST!)

Energy GeneraIon Part 5: Circuit


Titanium Dioxide

E

Unhappy.

=(

(Would rather sit here at lower energy)

The electron on the top left is in a high energy state and would like to return to

the unoccupied level on the lower right… but right now it can’t!

Energy GeneraIon Part 5: Circuit


Titanium Dioxide

E

We can offer the electron an external connection to the far side of the device

To Conductive Glass

From Conductive Glass & Graphite

(Graphite is a catalyst for the iodine redox reacIon)

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Energy GeneraIon


Titanium Dioxide

E

The difference in energy levels determines the amount of voltage the

device will produce!

ΔE = qV

Energy GeneraIon

Both the # of electrons (current) and the energy they come with (voltage) contribute to the overall power production of our device!

I is current.

P = IV

What is the equation for power?

.

The cycle is now complete!

3I I3 - -

Preparing Catalyst

Slide without Titania

Step Two: Building The Device

Titania Slide


Glass PlateWith Dye

Figure 6

A

B

C

Glass PlateWith Carbon

Glass PlatesAre Offset

AssembledSolar Cell

Binder Clips


Glass PlateWith Dye

Figure 6

A

B

C

Glass PlateWith Carbon

Glass PlatesAre Offset

AssembledSolar Cell

Binder Clips

X Iodide Solu'on Goes Here

X

TesIng Your Solar Cell

Projector

Multimeter

TesIng Your Solar Cell

Projector

Mul'meter

Current (A) Voltage (V)

Theoretical Power = Current x Voltage P = IV

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Thank You!

P=IV Current 1uA = 1x10-‐6 A Voltage 1mV=1x10-‐3V

P=IV Current 1uA = 1x10-‐6 A Voltage 1mV=1x10-‐3V

Let’s compare!

Team Name Current (uA) Voltage (mV) Power (nW) Power(W) Dr. Jin 0.1 22.5 2.25 2.25E-‐09 Solar Baby 130 290 37700 3.77E-‐05 Team Mareeps 170 66 11220 1.12E-‐05 Sunny Side Up 2 130 260 2.60E-‐07 Team DJ 7.1 250 1775 1.78E-‐06 Team Red 4.5 100 450 4.50E-‐07 Yoshi & Alina 23 177 4071 4.07E-‐06 It's Always Sunny At UCLA 16 50 800 8.00E-‐07 Team Raspberries 5 136 680 6.80E-‐07 Team Blue 70 115 8050 8.05E-‐06

Team 3 Tries

Team Name Current (uA) Voltage (mV) Power (nW) Power(W) Projector 39 230 8970 8.97E-‐06 In the sun 20 275 5500 5.50E-‐06

Let’s Compare!

Team Name Current (uA) Voltage (mV) Power (nW) Power (W) ★ 29 8 232 2.32E-‐07 No name 34 126 4284 4.28E-‐06 Israchel 29 271 7859 7.86E-‐06 Unknowns 80 306 24480 2.45E-‐05 Trojans 65 370 24050 2.41E-‐05 Bruins 95 700 66500 6.65E-‐05 Blank space 1 27 365 9855 9.86E-‐06 DK 36 406 14616 1.46E-‐05 Asian Squad 27 262 7074 7.07E-‐06 Blank space 2 40 170 6800 6.80E-‐06 Team 30 300 9000 9.00E-‐06 � 17 160 2720 2.72E-‐06 RA 30 132 3960 3.96E-‐06 (= 440 460 202400 2.02E-‐04 EIenne+Rohit 619 380 235220 2.35E-‐04

Debrief quesIons

•  What color do plants absorb? •  Why is ba[ery technology so important? •  What happens if you run the solar cell in reverse-‐ Apply a voltage to your solar cell

11/4/16 dyehsensiized%solar%cells%%...

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