Power from Juice

Blackberry Spinach Hybrid Solar Cells (DSSCs)

                         

Abstract:

A previous study (2009-18) showed DSSCs with anthocyanin dyes (from blackberries) could successfully power calculators and small motors with indoor lighting. The objective here is to expand to this previous work to include chlorophyll dyes (from spinach) and to compare the effectiveness of the cells when exposed to various light sources. The results indicate that while anthocyanin cells work well in all light sources, a hybrid cell with anthocyanin and chlorophyll has considerable promise when sunlight is the source.

 

Background:

DSSCs, known as Grätzel cells, are a new class of low-cost solar cells.1 They consist of a TiO2 electrode, light sensitize anthocyanin dye, an Iodide/iodine electrolyte and a carbon counter electrode.1 This type of cell is extremely promising because it is environmentally friendly and can be engineered into flexible sheets and carried everywhere as needed. These cells hit the market in 2010 and are forecasted to be a significant contributor to renewable electricity generation. 2

Goals:

• Fabricate 3” x 3” DSSCs using blackberry dye

• Learn how each DSSC components works

• Connect blackberry cells in series to run a calculator with just ambient light

• Connect blackberry cells in series to run a motor box in alternating charging/discharging modes

• Form hypotheses for investigation based on the light adsorption data of blackberry dye and spinach pigment, courtesy of Prof. Hu of Yale university

Discussion:

In the schematic of a DSSC, the dye acts as the photochemical pump which converts sunlight into electricity. Titanium dioxide is the electron acceptor and iodide transfers the electron.

A few prompt questions for consideration:

• What are the two metal oxides and their function used in the DSSCs?

• How are the processes in DSSCs and photosynthesis similar with regards to the energy transfer?

• How are the processes in DSSCs and cellular respiration similar in electron transfer?   

• Based on the light absorption data for blackberry and spinach can we design more efficient DSSCs?

• What could be done to produce more current or to increase the voltage output in DSSCs?

Hypotheses

According the light absorption data, blackberry dye absorbs green light. Spinach chlorophylls reflect green but absorb blue and red light. The blackberry dye and spinach chlorophylls are complementary to each other, therefore, a “hybrid” cell containing both photosensitizers should absorb the whole spectrum of visible sunlight.

             

Materials

• 3x3 Fluorine doped Tin Oxide conductive glass slides (donated by Harford Glass Company)

• Anthocyanins dye extracted from blackberries and Chlorophylls extracted from spinach

• Titanium Dioxide (purchased from Institute of Chemical Education)

• Iodide/Iodine solution (purchased from ICE)

• DI water, Acetic acid pH 3-4, Ethanol, Triton x100 solution

• Carbon soot counter electrode

Procedures  http://www.youtube.com/watch?v=9KhFPwag_T8  

Data Table & Analysis: Link

Conclusion

Based on the results, one can draw many conclusions. First, one can see that the source of light is an important consideration when designing solar cells. For example, the spectrum of light frequencies of indoor lighting is different than for natural sunlight. Different dyes absorb different light frequencies. An example of this is the solar cell with blackberry dye which produces significantly more power with indoor light, (an overhead projector or a light box,) than a cell with only spinach dye.  This is because the anthocyanin found in blackberries can absorb the indoor light and release electrons, producing a current/power. On the other hand, the spinach dye, which contains chlorophylls, does not absorb but tends to reflect light of this frequency and so the power output is low. However, the results switch when the solar cells were brought into the sunlight where the solar cells coated with spinach dye outperformed those with blackberry dye. This is because the chloroplasts in the spinach readily absorb sunlight, create ATP, and excite the electrons. The best results, however, were obtained from a hybrid cell that contained both blackberry and spinach dyes. These hybrid cells absorb light over a wider range of frequencies than the individual blackberry or spinach cells.  

Although the results appear to be conclusive, one must be cognizant of errors that could have taken place during the production of the solar cells. For example, there might be discrepancies in the individual cells. One cell might have a better titanium dioxide coating than another. Also, there may also be variations in the amount of dye in each cell. Some cells may “dry out,” or contain more or less of the needed iodine. Nevertheless, in order to minimize these errors, several cells were used and their results were averaged. Given this, in proceeding this way, it should have produced more reliable results.

Credit

Dr. Labowsky P1 Chemistry Honors

Daniel Bergman, Eunice Cha, Kyle Conenello, Matthew E. De Meulder, Patrick A. De Meulder, Frank P. Dunne, Ruby H. Gondris, Charles Healy, Anika Joshi, Alexandria Kenney, Payton A. Kliesch, Yeonji Lee, Caroline Loscalzo, Aum Mundhe, Chloe Nam, Joseph Peruyero, Logan E. Richman, Ryan M. Schnure, Catherine Tepper, Carina Trama, Janice K. Yoon

Acknowledgement

• Mr. Mike Reidy of Hartford Glass Company Co. Inc., Hartford, Indiana, has donated of 3” x 3” conductive slides every year since 2010. His generous support enables us to build powerful solar cells that can run calculators with ambient light at Super Science Saturday.

• Professor Shu Hu of the Chemical & Environmental Engineering, Department at Yale University provided us the dye light absorption data as part of the NSF high school outreach program 2019.

• Dr. Peter Lindner and Dr. Ishan Wathuthanthri of Stevens Institute of Technology GK12 program 2009-2011

Extra Information 

Class Powerpoint: Presentation