Electronics Applications in Nanotechnology Copper Oxide Solar Cells

Image by HighPoint Learning Gather the tools needed for the activity. Cut the copper sheet into equal strips. Each group gets two strips of copper. One is to be burned on a hot plate, Bunsen burner or torch. (The hot plate takes the longest; the torch is the fastest) The other copper strip is left clean.

Image by HighPoint Learning Heat one of the strips of copper until it becomes red hot.

Image by HighPoint Learning A clean copper strip leaves fewer impurities.

Image by HighPoint Learning Allow the copper strip to cool. The black substance formed is called cupric oxide. The cupric oxide will flake off because it does not shrink at the same rate as the rest of the copper strip.

Image by HighPoint Learning The flakes pop off leaving the cuprous oxide layer exposed.

Image by HighPoint Learning Here are a few examples of the results.

Image by HighPoint Learning Assemble the cell by placing the copper oxide strip and the clean copper strip in salt water. Attach the volt meter and record the results. (0.05V – 0.25V) Attach the microammeter and record the results. (0.125mA - 0.05mA) When the sun hits the cuprous oxide, it releases electrons into the water. The salt water acts as a conductor and transfers the electrons to the clean copper sheet. There is a positive charge on the cuprous oxide (absence of electrons) and a negative charge on the clean copper (excess of electrons).

Image by HighPoint Learning

Calculate and record the Power Power(Watts) = Voltage(Volts) x Current(Amps) Measure the Surface Area of the copper oxide Area(meter2) = Length(meter) x Width(meter) The power calculated should be extremely small.

Efficiency = _______________% Power of solar cell =______________ W Surface Area of the copper oxide = ______m2 Sun’s Energy = 1000 W/m2 Calculate the Efficiency of the cell %Efficiency = Power(watts) Sun’s Energy(Watts/meter2) x Surface Area(meter2) Efficiency = _______________% Were our cells very efficient? No What could we change to make them more powerful? Change material, increase area, focus more light on the cell How do you think that the copper oxide cell compares to other cells?

Image courtesy National Renewable Engergy Laboratories Our cells are similar to the ones marked in green Where does our copper oxide solar cell fit on this chart? Is our cell very efficient compared to others? Scientists are still exploring copper oxide and other inefficient semiconductors as a substance for solar cells. New materials and arrangements are leading to efficiencies as high as 40%. What can scientists do to increase power from the copper oxide solar cell? Image courtesy National Renewable Engergy Laboratories

Compare the Surface Areas of these cells Images by HighPoint Learning r =1.25 h=1.5 3 3 3 3 A= length x width = 9 A= length x width + 2πrh = 20.78

Image by HighPoint Learning Although the Efficiency should stay the same, increasing the Surface Area is a valid strategy to make an inefficient cell usable. r =.125 h=1.5 3 3 A= length x width + 2πrh x64 = 84.4

%Efficiency = Power(watts) ÷ Sun’s Energy(Watts/meter2) x Surface Area(meter2) Image by HighPoint Learning With the sun’s energy and the %Efficiency remaining the same, an increase in Surface Area should increase the power. A material that yields 1% efficiency theoretically could increase the Power by a factor of 10 by growing columns on the surface. 0.9W 2.078W 8.44W

By using nanotechnology processes to increase the surface area of the solar cell, scientists can get more energy from the same size cell. By using better material combinations, multiple junctions and increasing the surface area by using nanowires scientists are finding more promising results. cc by Kristian Molhave

Dye Sensitized Solar Cells In dye sensitized solar cells, nano-crystaline titanium dioxide are coated in dye. (The small size of the titanium dioxide increases the surface area for the dye) The light hits the dye which gives electrons to the titanium dioxide. The electrons go though the circuit and back to the base electrode. Electrons then goes through the iodine molecule and back to the dye. cc by Ronald Sastrawan cc by M.R. Jones

How is nanotechnology being used in solar applications? What are some of the new materials in solar cells? What are some new strategies being used in solar cells?

This module is one of a series designed to introduce faculty and high school students to the basic concepts of nanotechnology. Each module includes a PowerPoint presentation, discussion questions, and hands-on activities, when applicable.   The series was funded in part by:   The National Science Foundation Grant DUE-0702976 and the Oklahoma Nanotechnology Education Initiative   Any opinions, findings and conclusions or recommendations expressed in the material are those of the author and do not necessarily reflect the views of the National Science Foundation or the Oklahoma Nanotechnology Education Initiative.  

Image Credits Jones, M.R. (Designer). Dye Sensitized Solar Cell Scheme.png [Digital Diagram]. Wikimedia Commons (commons.wikimedia.org) Molhave, Kristian (Professor) and Martinsson, Thomas (Designer), Epitaxial Nanowire Heterostructures SEM image.jpg [Scanning Electron Microscope image], United Kingdom, Wikimedia Commons (commons.wikimedia.org) National Renewable Energy Laboratory (Designer). Carbon Nanotubes.jpg [Digital Image]. United States. Wikimedia Commons (commons.wikimedia.org) Sastrawan, Ronald. (Designer). Dye.sensitized.solar.cells.jpg [Digital Image]. Wikimedia Commons (commons.wikimedia.org)  

References Berger, Michael. (2010) References Berger, Michael. (2010). Improved design for dye-sensitized solar cells includes quantum dot antennas. NanoWerk. Retrieved from http://www.nanowerk.com/spotlight/spotid=15000.php Grätzel, Michael. (2003). Dye-sensitized solar cells. Journal of Photochemistry and Photobiology C: Photochemistry Reviews. Issue 4. Pages 145–153. Williams, Linda and Dr. Wade Adams. (2007). Nanotechnology Demystified. [Kindle Version] doi: 10.1036/0071460233 Wilson, Michael, Kanangara, Kamali, Smith, Geoff, Simmons, Michelle, & Raguse, Burkhard. (2004). Nanotechnology: Basic Science and Emerging Technologies. [Kindle Edition] Retrieved from http://www.amazon.com