THE OPTIMIZATION OF DYE-SENSITIZED SOLAR CELL

EFFICIENCY THROUGH ANALYSIS OF ANTHOCYANIN AND

CHLOROPHYLL-BASED DYES

By: Margaret Pan, Margaret Tian, Shraddha Rathod, Vany Nguyen

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Engineering Goal

To investigate sources of natural anthocyanin or chlorophyll-based

dyes that produce the most efficient dye-sensitized solar cell.

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Problem and Objective o Sources of inexpensive, reliable, and sustainable energy have been

greatly sought after in recent years.

o While the most efficient dye-sensitized solar cells employing noble-based dyes have reached efficiencies of approximately 12%, these are impractical and costly due to limited resources.

o Cells created from organic materials are more environmentally-friendly and cost effective and have attained efficiencies of 7.9%. [3]

o In this study, we explored the use of organic sources of chlorophyll and anthocyanin in devising an inexpensive method of producing solar cells that efficiently harness light energy.

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Hypothesis

A solar cell containing both anthocyanin and chlorophyll dyes

would yield the most efficient solar cell due to the combined absorption

capabilities of the molecules.

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Procedure Summary

1) Made dyes and generated absorbance spectra

2) Constructed solar cells

3) Tested efficiency

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Dye Selection o In order to choose the dyes that may produce the most

efficient solar cells, we selected literature sources that include the greatest amount of chlorophyll and anthocyanin.

o The dyes that we obtained were:

Chlorophyll Anthocyanin

Clover Blueberries

Damiana Nandina Berries

Celery Eggplant

Broccoli Blackberries

Lettuce Bell Pepper

-- Concord Grape Juice

Fig. 1

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Dye Preparation o Anthocyanin Dyes: crush ~15 g of the material using a mortar and pestle in 40 mL of

a methanol/acetic acid/water solution that was in a 25:4:21 ratio by volume

the mixture was passed through filter paper repeatedly until a clear liquid could be obtained

o Chlorophyll Dyes: place the samples (except Damiana) in boiling water for 30

seconds to denature enzymes that would otherwise cause chlorophyll degradation

Crush each sample using a mortar and pestle in ethanol and again filtered until the extract was clear

For Damiana: crush the dry leaves and deposit this powder in a 4 oz glass bottle half-filled with ethanol and agitated until the ethanol had taken on a dark green tint; pass the dye through a filter. 7

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Dye Testing o We tested each dye using UV-Vis absorption spectroscopy

to choose the dyes (2 chlorophyll and 2 anthocyanin) with the greatest range of absorption.

o We analyzed the graphs based on the breadth of the curves and not the magnitude. The breadth of the curve represents the wavelengths attributed to each dye, while the magnitude is only attributed to concentration.

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Anthocyanin Spectrum

Fig. 2

9 Wavelength (nm)

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Chlorophyll Spectrum

Fig. 3

10 Wavelength (nm)

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Choosing Dyes o After examining the chlorophyll and anthocyanin absorption

spectrums we deduced that the following dyes had the best ranges of absorption:

• Anthocyanin: blueberry and nandina berry dyes

• Chlorophyll: clover and damiana dyes

o In order to obtain the most inclusive spectrum, we chose to mix the top chlorophyll and anthocyanin dyes

o The hybrid dye showed to absorb in both the chlorophyll and anthocyanin wavelengths

Fig. 4

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Top Dyes

Fig. 5

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Solar Cell Setup [6]

1) Make TiO2 paste from dry powder and nitric acid.

2) Coat the conductive side of a glass slide with TiO2 paste and anneal in kiln.

3) Carbon coat the conductive side of the complementary slide over an open flame.

4) Place the TiO2-coated slide in a petri dish of dye and leave for designated amount of time.

5) Sandwich the dyed and carbon coated slides and clip with binder clips.

6) Add iodide electrolyte solution between the slides

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Solar Cell Construct

Fig. 6

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Measurements o In order to minimize the influence of environmental factors on

the accuracy of our data, we tested our solar cells in a controlled indoor environment.

o We placed the solar cell 36 inches from a 660 Watt incandescent bulb.

o We set up a circuit that we connected to our solar cell and measured the current and voltage using multimeters and a potentiometer [6]

o Our circuit setup:

Fig. 7 [6]

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Data Processing

o To compare the effectiveness of each solar cell, we calculated the average

efficiencies.

o The power density of each cell was determined using the experimentally-

determined values of current and voltage.

o We calculated the power density of the lamp used and then the efficiency

of each solar cell.

o We then compared the percentages of the different types of solar cells in

order to determine the most suitable dye for constructing solar cells.

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Example Data Chart

Voltage (mV) Current (uAmp) Current Density

(mA/cm2)

Power Density

(mW/cm2)

54 55 0.014 0.00074

152 48 0.012 0.0018

260 40 0.010 0.0026

283 35 0.0088 0.0025

299 30 0.0075 0.0022

308 26 0.0065 0.0020

317 22 0.0055 0.0017

323 19 0.0048 0.0015

326 17 0.0043 0.0014

327 14 0.0035 0.0011

331 11 0.0028 0.00091

333 9 0.002 0.0007

334 7 0.002 0.0006

334 6 0.002 0.0005

Damiana Solar Cell Results

Fig. 8

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Initial Calculations

o In order to consider the lamp’s light intensity in our calculations, we measured the lux of the lamp using a Vernier Light Probe. We used the equation below to convert Lux into Watts:

o We then took the value obtained from above to measure the irradiance of the lamp:

o From this, we calculated the percent efficiency of each cell through the following equation:

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Final Numbers Lux Surface Area

(m^2)

Luminosity

Efficacy (lm/W)

Lamp Power

Intensity (W)

Irradiance

21,306 0.41 15.5 560 0.034

Values for Efficiency Calculations

Average Conversion Efficiencies of Solar Cells

We used the formulas from the previous slide and the values from above to come upon the following percent efficiencies:

Fig. 9

Fig. 10

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Blueberry Nandina Clover Damiana Hybrid

Average Efficiencies

1.5

.65

1.2

1.7 1.6

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Discussion

o Contrary to our hypothesis, we found that cells produced from Damiana dye had the greatest power density output.

o Though the hybrid dye had a greater range of absorption, the efficiency measure of this cell was similar to that of pure anthocyanin. This is a likely result of the nature of TiO2 dye-adsorption on a molecular level.

o The anthocyanin dye molecules absorbs to the porous TiO2 within 15 minutes of staining, therefore occupying the majority of the slide, leaving little to no surface area for the comparatively larger chlorophyll molecules, which take approximately 24 hours to fully bond.

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Conclusions

o Based on relative efficiencies, the damiana chlorophyll dye formed the most effective solar cell.

o Solars cells synthesized from chlorophyll dyes most closely mimic the sun-harnessing power of nature's plants.

o As we could not account for all procedural inconsistencies, even solar cells created from the same dyes showed slight variance in power output.

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Future Work o Decrease rate of cell degradation by confining the Iodide electrolyte

in the cell

• place a layer of parafilm over the TiO2 and dye layers to seal off iodide solution and prevent evaporation.

o Analyze amount of dye adherence to TiO2

• use a thin-film of TiO2 and run it through a UV spectrum

• after dyeing the TiO2, place the slide in a solution of a known concentration and measure the change in that solution

o Different dyeing methods

• dyeing the hybrid cell with chlorophyll before anthocyanin

• dyeing in layers

o Increase procedural uniformity

• larger sample size

• more trials 22

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Bibliography • [1] A., Sharifi, and Hassani B. "Extraction Methods and Stability of Color Extracted from

Barberry Pigments." International Journal of AgriScience 2(4) (2012): 320-27. Web. <http://www.inacj.com/attachments/section/17/Temp%20April%202012-458%20Akram%20Sharifi%20C%20E%20C%20P%20(pp%20320-327).pdf>.

• [2] Berg, Jeremy M. "19.2.1 Photosynthetic Bacteria and the Photosynthetic Reaction Centers of Green Plants Have a Common Core." Light Absorption by Chlorophyll Induces Electron Transfer. U.S. National Library of Medicine, 18 Feb. 0000. Web. 05 Mar. 2013.

• [3] Brian, O'Reagan, and Gratzel Michael. "A Low-cost, High-efficiency Solar Cell Based on Dye-sensitized Colloidal TiO2 Films." Letters to Nature 353 (1991): 737-39. Web. 7 Jan. 2013. <http://chem.rutgers.edu/sites/default/files/353737a0.pdf>.

• [4] Cherepy, Nerine J.; Smestad, Greg P.; Grätzel, Michael; Zhang, Jin Z. (1997)."Ultrafast Electron Injection: Implications for a Photoelectrochemical Cell Utilizing an Anthocyanin Dye-Sensitized TiO2 Nanocrystalline Electrode". The Journal of Physical Chemistry B 101 (45): 9342–51.

• [5] Excited-State Electron Transfer in Anthocyanins and Related Flavylium Salts. Palmira Ferreira da Silva, João C. Lima, Frank H. Quina, and Antonio L. Maçanita. The Journal of Physical Chemistry A 2004 108 (46), 10133-10140

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Bibliography (cont.) • [6] Fanis, Linda. "The Nanocrystalline Dye Sensitized Solar Cell." Nanocrystalline Solar

Cell Kit: Recreating Photosynthesis. 2nd ed. Madison, WA: University of Wisconsin Board of Regents ,1998. 18-23, 31-48. Print.

• [7] Gallik, Stephen, Ph. D. "Anthocyanin." N.p., 2011. Web. <http://cellbiologyolm.stevegallik.org/anthocyanin/page18>.

• [8] Huizhi Zhou, Liqiong Wu, Yurong Gao, Tingli Ma, Dye-sensitized solar cells using 20 natural dyes as sensitizers, Journal of Photochemistry and Photobiology A: Chemistry, Volume 219, Issues 2–3, 15 April 2011, Pages 188-194, ISSN 1010-6030,10.1016/j.jphotochem.2011. 02.008. <http://www.sciencedirect.com/science/article/pii/S1010603011000700>.

• [9] Patricia, Shapely. "Absorbing Light with Organic Molecules." Absorbing Light with Organic Molecules. University of Illinois, 2012. Web. 05 Mar. 2013. <http://butane.chem.uiuc.edu/pshapley/GenChem2/B2/1.html>

• [10] Qin, Chuan-guang, Yang Li, Weining Niu, Yan Ding, Xiaoya Shang, and Chunlan Xu. "Composition Analysis and Structural Identification of Anthocyanins in Fruit of Waxberry." Czech Journal of Food Sciences 29 (2011): 171-80. Web. <http://www.agriculturejournals.cz/publicFiles /37435.pdf>.

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Acknowledgements

o North Carolina School of Science and Mathematics

o Dr. Halpin

o Colleagues at Research in Chemistry Class

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