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Nagilthes Muthu-Increasing the life span of polymer solar cell

My analytical problem is about polymer solar cells. Currently, silicon based solar cells are widely used when it comes to solar cells. Many researches are being done regarding polymer solar cells because they offer some advantages. The cost to manufacture polymer solar cells is lower(1). Besides that, polymer solar cells are flexible(1). They may be used in clothes(1). Polymer based solar cells would also be lighter because polymer is like plastic. Unfortunately, the current polymer solar cells have a short life span(1). The presence of air and changes in temperature shortens the life time of polymer solar cells(2). Illuminations as in light or dark tend to degrade the polymer solar cell as well(1). My central hypothesis is to increase the life span of polymer solar cells. The main analyte are polymers. The matrix would be the solvent where the polymer is dissolved in.

1) Rasmus, Larsen, Petersen and Lund. Polymer solar cells. Aalborg University. (2006)

2) Janssen. Introduction to polymer solar cells. Eindhoven University of Technology, The Netherlands.

UV-Vis absorption spectrometry.

I am going to refine my hypothesis. I am focusing on the morphology of solar cells. Morphology is the study of the architectural structure of the polymer. If morphology can be improved, the life span of solar cells can be improved. In solar cells, two types of polymer would be mixed in a solution and spin-cast. The solution may evaporate and the remaining polymers act as charge donor and charge acceptor respectively. It had been found that the efficiency of solar cell has increased when chlorobenzene used as solvent instead of toluene. UV-Vis absorption spectrometry can be used to identify if any interactions happen between the polymers and solvent. The maximum wavelength value of chlorobenzene for UV-Vis absorption spectrometry is 310nm. If the wavelength seems to vary, then interaction between the solvent and the polymers can be suspected. Other than that, whenever, the polymer gives out charge, they tend to crumpled up among it self. Meaning the interaction between the two polymers seems to be decreasing. This can be observed using transmission electron microscopy (TEM). When the interaction between both of the polymers decreases, the solar cell can no longer be used. The key to improve the life span of solar cell is to maintain the polymers from crumpling up to it self respectively. The polymer pairs that are commonly used are P3HT/PCBM and MDMO-PPV/PCBM.

Thompson, B. C.; Frechet, J. M. J.; Polymer-Fullerene Composite Solar Cells. Angew. Chem. Int. Ed. 2008, 47, 58-77

For some reason my comment on F-9- Reduction of Mesotrione in Aquifers and Surface Waters doesn't appear. So, I'll post my comment here:

This analytical problem is almost similar as mine because in this problem, the pseudo-steady state reactivity is being studied. In my problem, I would like to maintain a good morphology of the polymers. Meaning I would like to find ways where the polymers would be stable and would not degrade by crumpling up to itself respectively. Besides that, in this problem transmission electron microscopy has been used. And I am also planning to use that method to investigate my problem.

Similar Analytical Problem.
Matt Wasilowski-Analytical Problem-Biodiesel from waste water sludges.
I believe the above mentioned analytical problem would be slightly similar to mine. The analytes being studied in this problem are lipidic material present and the biodiesel monoalkl ester of interest. These analytes are found in the matrix of original filtered waste water feedstock and the final product stream.
I believe this problem is slightly similar to mine because it involves Green Chemistry. In this problem, methods are developed to find ways to reuse waste water. I believe this would be beneficial to the environment. In my problem, I'm trying to increase the life span of polymer cells. If polymer solar cells are widely used one day, I believe it would be an alternative way to get clean energy. This corresponds to Green Chemistry.
The studies would be different in the sense that, the analyte in the above problem, are organic materials while in my problem they are polymers.

Blog 4.
1. Hypothesis: Morphology of P3HT/PCBM depends on the ratio they are prepared in and the temperatures they are in.

Studies: (A) Determine the highest temperature that P3HT and PCBM could withstand. (B) Prepare solutions of them with different weight ratios (ex: 1:1, 1:2, 1:4, etc) and spin cast them. Heat them up at different temperatures. Then cool them down at different temperatures to see if there are any changes to the morphology. (C) Identify the blend ratio that is most stable with the largest range of temperatures. (D) Find the maximum and minimum temperatures at which the selected blend ratio would be stable.

2. ITO coated glass would be cleaned. Solution of P3HT/PCBM would be prepared in various weight ratios in chlorobenzene. Then the solution would be spin cast on the glass. Therefore, the analyte would be occupying the most space on the glass. In case the solvent does not dry out completely, that might become part of the matrix. But, I don't think that would be the case because the solvent should all be evaporated during spin-cast. Other than that, the glass where the solution would be spin-cast would be the background.

I forgot to put the reference when I answered the previous blog. Here is the reference:

Vanlaeke, P.; Swinnen, A.; Haeldermans, I.; Vanhoyland, G.; Aernouts, T.; Cheyns, D.; Deibel, C.; D'Haen, J.; Heremans, P.; Poortmans, J.; Manca, J.V. P3HT/PCBM bulk heterojunction solar cells: Relation between morphology and electro-optical characteristics Solar Energy Materials & Solar Cells 90 2006, 2150-2158.

Blog 5.
Based on the papers I have read so far, I have not come across fluorescence method being used to study P3HT. Therefore, I am answering #4 for this blog.
In the FTIR spectrum, the thiophene ring that corresponds to P3HT shows out of plane deformation of C-H at 819cm-1 (wavenumbers). This is used to study the charge transfer effect in P3HT. A new band develops at 835cm-1 for the 1:1 P3HT:PCBM film. When the amount of PCBM is increased, the intensity of the band increases as well. This band is due to the charge transfer between sulfur atom from P3HT molecule to PCBM molecule. Therefore, the bands that I should be looking for in IR spectrum would be the bands at 819cm-1 and 835cm-1. Besides that, I should be taking the IR of P3HT and PCBM on their own and the IR once I have mixed them in the ratio of interest. Later on, the IR of this mixture would be taken at different temperatures. And these IR spectrums can be compared to the IR spectrum of P3HT (on its own), PCBM (on its own), and the pristine mixture that was initially prepared to observe any changes that may occur on the spectrum.

Shrotriya, V.; Ouyang, J.; Tseng, R. J.; Li, Gang.; Yang, Y. Absorption spectra modification in poly(3-hexylthiophene):methanofullerene blend thin films Chemical Physics Letters 411 2005 138-143

Blog 6.
2. This is poly(3-hexylthiophene-2,5-diyl). It is commonly abbreviated as P3HT. In a polymer, this molecule is repeated creating a chain like structure. This is Phenyl C 61 butyric acid methyl ester. It is commonly abbreviated as PCBM.


3. I do not think I would need to calibrate my instrument. The spectrum that I would take with each sample would be compared to the spectrum of the sample when it was initially prepared.
Company that sells P3HT and PCBM: Sigma Aldrich
P3HT: Product number: 445703-1G; Quantity: 1g in glass bottle; Price: $590.00
PCBM: Product number: 684457-100MG; Quantity: 100mg in glass bottle; Price:

Blog 7.
The analyte that I would be looking at mainly is P3HT. Its molecular weight is not really fixed. People had studied the temperature dependent x-ray diffraction and reflectivity measurements using rr-P3HT with molecular weight of 45000 g/mol. The mass analyzer I would be using is MALDI-TOF. Example of mass spectrum:
View image

MALDI-TOF mass spectrum of regioregular P3HT-NH2

Xu. Jun; Wang. J; Mitchell. M; Mukherjee, P; Jeffries-EL. M; Petrich. J; Lin. Z. Organic-Inorganic Nanocomposites via Directly Grafting Conjugated Polymers onto Quantum Dots J. AM. CHEM. SOC. 2007, 129, 12828- 12833
Sigma Aldrich

Blog 9

Size exclusion chromatography would be the most preferred method. This chromatography is best for analyzing proteins, polymers, and generally any big sized molecules. The column would be used is a mixed-C PL-Gel (PL) column. This column could be purchased from Thomas Scientific. Its manufacturing number is 79911GP-110. It costs $677.08/ EA. Detector would be used is Refractive Index detector (Shodex).

1) S. Bertho et al. / Organic Electronics 10 (2009) 1248-1251
2) Journal of The Electrochemical Society, 156 _4_ K37-K43 _2009_
3) Macromolecules, Vol. 43, No. 10, 2010

Blog 10.
1. Preferred technique: UV-Visible spectroscopy.
2. Analytical problems that have selected the same technique: Nanoparticles Accumulate in the Food Chain, Comparative analysis of arbutin and tranexamic acid in skin whitening products, Nitric oxide and muscle growth.

Blog 11.
The best type of CE for my problem is CGE because I am dealing with polymers. CZE is good for protein. CIEF is normally used for proteins and peptides.
Buffer used is PEDOT:PSS layer. Its pH range is 1 to 2. Capillary used would be coated capillary.
The detector would be used is absorption spectrometry. This is because P3HT and PCBM have been usually monitored using their absorption.

Lecture notes.
Elschner, A., Kirchmeyer, S., Lovenich, W., Merker, U., Reuter. Knud., PEDOT Principles and Applications of an Intrinsically Conductive Polymer; Taylor & Francis Group, LLC, Florida, 2011; p 220.
UCDavis ChemWiki.

Blog 13
Since P3HT and PCBM are involved in solar cell, they should be electroactive. Galvanic cell could be used to identify P3HT and PCBM when they transfer electrons to each other.


Blog 13. More details for questions 2 and 3. References? -0.75 pt.

Blog 9. What is the MW range of analytes that the selected column can separate (-0.1 pt).
Blog 10. Good answer.
Blog 11. I do not understand the acronyms describing the running buffer (-0.1 pt).

Blog 8 ? (- 1 pt)

Blog 6 is OK.
Blog 7. The MS example is very different from the MW range that you reported. Other types of mass spectrometry? (-0.2 pt).

Blog 8.
1. Polymer solar cell is composed of many layers. Since, I would like to study the morphology of the P3HT:PCBM pair, I would prepare a layer that consist both of the polymers only. The best solvent used to dissolve that pair of polymers thus far is chlorobenzene. The ratio used would be 1:1 (wt.%). After the solution is prepared, I’ll pipette some solution into a glass slide. Then the glass slide would be spin-cast at 700rpm. Once a thin layer had formed on the glass layer, the opposite side of that glass layer would be wiped with methanol to remove any residue on that side of the glass. I do not want any unwanted residue to interfere with the readings that I would take further down the road.

2. When I am going to prepare my sample, I would try to buy the polymers in their cleanest condition possible from the company. However, if I had to isolate the polymers that I want, I would use standard column chromatography (silicagel, eluent: chloroform/toluene 1:1) to separate the PCBM from other by-products that formed during its preparation. As for the P3HT, it can be cleaned using Analytical Size Exclusion Chromatography (SEC). This would be performed using a Spectra series P100 (Spectra Physics) pump equipped with 2 mixed-B columns and a Refractive Index detector at 60C. Chlorobenzene would be used as the eluent with a flow rate of 1ml/min.

Kim, J.; Kim, S.; Lee, H.; Lee, K.; Ma, W.; Gong, X.; Heeger, A. New Architecture for High-Efficiency Polymer Photovoltaic Cells Using Solution-Based Titanium Oxide as an Optical Spacer Adv. Mater. 2006, 18, 572–576

Bertho, S.; Oosterbaan, W.; Vrindts, V.; Jan, D.; Cleij, T.; Lutsen, L.; Manca, J. Vanderzande, D. Controlling the morphology of nanofiber-P3HT:PCBM blends for organic bulk heterojunction solar cells Organic Electronics 10 (2009) 1248–1251

Lenes, M.; Wetzelaer, G.; Kooistra, F.; Veenstra, S.; Hummelen, J.; Blom, P. Fullerene Bisadducts for Enhanced Open-Circuit Voltages and Efficiencies in Polymer Solar Cells Adv. Mater. 2008, 20, 2116–2119

Good answers for Blogs 4 and 5.

BLOG 3- The answers for parts (b) and (c) lack detail. (-0.5 pt).

BLOG 2 - Revise your entry. Prepare a succinct answer for the UV-VIS part, different from your previous statement about the hypothesis. You do not need to talk about TEM here. Once you have done this change notify Chad so that he releases your grade. Thanks. Edgar

See other comment regarding the posting on another entry.
Molar absorbtivity or approach to determine it? (-0.3 pt)

Revise your hypothesis. What you describe as hypothesis is the goal of your research. (-0.2 pt).

I do not believe that solvent is the matrix. These polymers are not in a solvent when they are part of solar cells. (-.2 pt).