M.A. Rose, 2008

Leveraging the Experimental Method to Inform Solar Cell Design

Mary Annette Rose Jason Ribblet Heather Hershberger

International Technology Education AssociationFebruary 22, 2008, 2:00-2:50, Room 251E

M.A. Rose 2008

Science-Technology Enterprise

Images: The School of Science and Engineering, The University of Waikato. Retrieved http://sci.waikato.ac.nz/about_the_school.shtml

Symbiotic Relationship

Mutual Dependence

M.A. Rose 2008

Thin-Film Solar Cells

Collaboration of the National Renewable Energy Laboratory & Heliovolt to develop a solar cell using a copper-indium-gallium selenide (CIGS) semiconductor.

Scientific challenge: to understand the chemistry and microscopic structure of the material in order to optimize its electrical properties.

Engineering challenge: develop a reliable manufacturing process—akin to a printing process— that produces standard size modules (15 & 30-cm wide).

Bullis, K., (2007). Making cheaper solar cells. Technology Review. Wednesday, September 12, 2007. Retrieved January 23, 2008, from http://www.technologyreview.com/Energy/19369/page1/

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Challenge for Technology Education

Science

Content & Process

Technology

Content & Process

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Presentation Goal

Photochemistry Solar CellsInquiry:

Experimentation Design

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Cuprous Oxide Solar Cell

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Observing Phenomena

Stimulate intellectual curiosity

• What is happening in this system?

• What energy is at work here?• What are the inputs, processes,

and outputs of the system? • What happens if we block the

cell from the sun? • What happens when we

reverse the probes of the multimeter on the plates of the cell?

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Solar Cell: Photoelectric Effect Parts & Materials List

Component Function Parts Material Qty - Size

Case Water–tight transparent housing

Front/Back 1/8” Acrylic 2 pcs of 4 1/8”” x 4 1/8”

Sides/Bottom 1/8” Acrylic 1 pc of ½” x 12”

Plates Anode and Cathode

Cuprous OxideCupric Oxide

0.20” Copper, Unpolished

2 pcs of 3 7/8” x 5”

Salt Solution

Medium of ion exchange

Salt (NaCl reagent grade)

15% NaCL or 17.6 g

Distilled Water

85% H2O or 100 ml

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Challenge Students to…

• Take on the role of a photochemist

• Learn how solar cells convert light into electricity

• Inform cell design

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Photochemistry is…

• study of chemical reactions of molecules in excited states produced by the absorption of light energy, i.e., photon – infrared (700–1000 nm) – visible (400–700 nm)

– ultraviolet (200–400 nm) • electron transfer and ionization

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Challenge Students to…

• Take on the role of a photochemist

• Learn how solar cells convert light into electricity

• Inform cell design• Plan, implement, and

interpret an experiment

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Experiment: Method for Investigating Variables

Cause Effect

IndependentVariable

Dependent Variable

To what extent does the distance from the light source effect the power production of solar cells?

TreatmentVariable

Outcome Variable

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What variables influence the power output of the cell?

List Variables& Identify Elements

• Concentration of salt solution

• Distance between plates (E)

• Surface area of plate (Cu2O and CuO)

• Type of light (frequency)

• Intensity of the light• Thickness of copper

plate

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What question might we experimentally test?

Variables Question• Concentration of salt

solution• Distance between plates (E)• Surface area of plate (Cu2O

and CuO)• Type of light (frequency)• Tilt of cell to light source• Intensity of the light• Thickness of copper plate• Type of plate

How does the concentration of the salt solution (IV) effect the electrical power output (DV) of the cell?

How does the concentration of the salt solution (IV) and the tilt of the cell (IV) effect the electrical power output (DV) of the cell?

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Form Teams and Assign to Treatment Conditions

Treatment Group 1

5% Solution

Treatment Group 2

15% Solution

Treatment Group 3

25% Solution

TedLauraElsa

Howard SallyFrank

FranTed

Harry

SamBobInga

MarthaRex

Harris

BillJeanRemi

1 2

3 4

5 6

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Day 2 & 3: Manufacture CellsSpecifications Top/Back: C x B Side: D x (2B+C) Plate: F x A A = 5”B = 4 1/8”C = 4 1/8”D = 1/2”E = 3/16”F = 3 7/8”

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Homework: Literature Review

Students discover more about…

semi-conductive materials, the photoelectric effect,

the interaction of energy and materials,

and

solar (photovoltaic) cells.

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Day 2 & 3: Manufacture Cells Process Sheet Metal

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Chemical SafetyHazards Safety PracticesNitric Acid (oxidizing agent)

corrosive and reactive, teacher should prepare and handle the solution,

store alone in storage cabinet

Acrylic Adhesive methylene chloride volatile: inhalation hazard

skin irritant

Cupric oxide (black powder) skin irritant

Handle in a well-ventilated area.

Wear chemical splash goggles.

Wear neoprene gloves and clothing protection.

If directly exposed, flush the affected area with water.

For laboratory safety, see the National Institute for Occupational Safety (NIOSH, 2006).

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Heat Copper Plate

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Heat Promotes Copper Oxidation

Type Formula Color Photoelectrical Property

Copper I oxide cuprous oxide Cu2O Red

Photovoltaic

Copper II oxide cupric oxide CuO Black

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Layer of Cupric Oxide (Black)

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Acrylic Processing

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Assemble the Case

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Test for Leaks

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Day 4: Procedure for Data Gathering

Stimulate planning• What procedure will we use

to test the cells? • How can we assure

systematic and consistent testing conditions?

• Why does a scientist strive for consistent experimental conditions?

Set-UP

Measuring

Recording

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Procedure for Data GatheringSetting-up Measuring Recording

1. Specify light source

2. Relative position of cell to light source

3. Charging the cell

1. Attaching alligator clips/probes to multimeter

2. Adjusting function & range

3. Reading meter

Dependent DV-3

DependentDV-2

DependentDV-1

TreatmentIV-2

TreatmentIV-1

Voltage(mV)

3/8”25%6

3/16”25%5

3/8”15%4

3/16”15%3

3/8”5%2

3/16”

Distance b/w Plate(IV2)

5%

(IV1)

1

Power(mW)

Current(μA)Team

Dependent DV-3

DependentDV-2

DependentDV-1

TreatmentIV-2

TreatmentIV-1

Voltage(mV)

3/8”25%6

3/16”25%5

3/8”15%4

3/16”15%3

3/8”5%2

3/16”

Distance b/w Plate(IV2)

5%

(IV1)

1

Power(mW)

Current(μA)Team

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Data Analysis

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Recording DataTreatmen

tIV-1

TreatmentIV-2

Dependent

DV-1

Dependent

DV-2

Dependent

DV-3

Team Salt

Solution(IV-1)

Angle of Test(IV-2)

Voltage(mV)

Current(μA)

Power(mW)

1 5% 30°

2 5% 45°

3 15% 30°

4 15% 45°

5 25% 30°

6 25% 45°

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Data Gathering

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Recording Data

Treatment

IV-1

TreatmentIV-2

Dependent

DV-1

Dependent

DV-2

Dependent

DV-3

Team Salt

Solution(IV-1)

Tilt(IV-2)

Voltage(mV)

Current(μA)

Power(μW)

1 5% 90° 22 88 1.94

2 5% 45° 10 74 0.74

3 15% 90° 45 346 15.57

4 15% 45° 29 282 8.18

5 25% 90° 40 216 8.64

6 25% 45° 30 192 5.76

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Power Output of Cuprous Oxide Cellby Salt Concentration and Tilt

1.94

15.57

8.64

0.74

8.1785.76

0

5

10

15

20

5% 15% 25%

Salt Concentration

mic

roW

att 90°

45°

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Interpreting the Results

• Level of salt in the solution impacts performance with best performance occurring at 15%

• Tilt impacts performance with 90° tilt (perpendicular) consistently position resulting in best performance

• The best performing combination of factors was a 15% solution at 90° tilt

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The Photoelectric Effect

Yaqoob, T. (n.d.). Photoelectric effect [Image]. John Hopkins University. Retrieved from http://www.pha.jhu.edu/~yaqoob/8m/lecture2/photoelectric_1.gif

h= Planck’s Constant v = frequency 1 eV = 1.6 x 10-19 joules

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Atomic States: Ground vs. Excited

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What is happening in the solar cell?

• Excitation of a Cu2O:• Negatively charged ions move through circuit, • Positively charged ions break free, and• Combine on the raw copper plate.

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Solid State PV Cell

Michell, R. (2000). A Seimens crystalline PV cell. WisconSUN. Retrieved from http://www.wisconsun.org/learn/learn_intro.shtml; Renewable Energy Works. (n.d.) Photovoltaics.[Image]. Retrieved 3/10/06, from http://www.renewableenergyworks.com/pv/PVDefn/PVDefn.html

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Learn More

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Let’s Make Connections & Review !!

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Alignment to National Standards

Standards for Technological Literacy (ITEA, 2000)

National Science Education Standards (NRC, 1996)

Inquiry & Experi-mentation

10. Students will develop an understanding of the role of troubleshooting, research and development, invention and innovation, and experimentation in problem solving.

As a result of the activities in grades 9-12, all students should develop:

Abilities to do scientific inquiry

Understanding about scientific inquiry

Energy 16. Students will develop an understanding of and be able to select and use energy and power technologies.

As a result of the activities in grades 9-12, all students should develop an understanding of:

Structure and properties of matter

Chemical reactions Interactions of energy and

matter

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Characteristics of Experimental Designs

1. Pose a research question which identifies the treatment (IV) and an outcome (DV) variable.

2. Select & assign a sample to treatment conditions

– Experimental group (Receives treatment)

– Control group (No treatment)

– Comparison groups (Different Levels of treatment)

3. Apply treatment to one or more groups

4. Control extraneous variables

5. Measure outcomes

6. Statistically describe and represent the data

7. Statistically test the hypothesis

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Inquiry is a Search for Understanding

• Spurred by intellectual curiosity • Process is characterized by …

– observing phenomena– asking questions and hypothesizing – systematically gathering and analyzing data– theorizing about the meaning of the

evidence• Enabled by objective, measurable, and

replicable methods

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Best Practices & Scaffolding

– Initiate intellectual curiosity – Ask questions, and encourage students to form questions – Provide increasingly more complex models (conceptual-to-realistic)

of the photoelectric effect– Provide visual examples and simulations of photochemical

processes– Provide access to diverse resources, e.g., chemistry and physics– Guide students through experimentation: sampling, hypothesizing,

identifying variables, planning procedures, analyzing data, interpreting data

– Require sense-making activities, such as collaborative discussion and the creation of cause and effect diagrams

– Require students to apply experimental findings to the re-design of a solar cell.

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Contact ….

Mary Annette RoseBall State University

arose@bsu.edu765-285-5648

http://arose.iweb.bsu.edu

M.A. Rose 2008M.A. Rose,

2008

Leveraging the Experimental Method to Inform Solar Cell Design

Mary Annette Rose Jason Ribblet Heather Hershberger

International Technology Education AssociationFebruary 22, 2008, 2:00-2:50, Room 251E