Two of the major problems that are commonly associated with solar cells today are the monetary cost and efficiency of this renewable energy source. However, one aspect which is commonly forgotten in determining the benefit of such a “green” energy source is the amount of waste which is produced from the processing of the solar cell. In particular, the processing of organic solar cells requires large amounts of solvents which can be harmful to the environment.
In the lab I am currently working in, Professor Vaccaro is exploring new methods to reduce the amount of solvent waste in the processing of organic compounds which can be used for different uses, mainly organic solar cells. His lab has explored the use of green solvents which come from natural sources and are biodegradable. This limits the damaging impact upon the environment.
In addition to this, they are using the green solvent in a process called flow chemistry. Most chemical reactions are conducted in a round bottom flask and require a lot of heat and solvent. This is known as batch chemistry which is inefficient and slow. In flow chemistry, the compound runs through a small tube with all the reactants needed for the reaction. The high pressures and heat capable in the flow tube allow for the reaction to proceed quickly and efficiently with small amounts of solvent.
Another source of increased solvent use is in removing of the impurities in the products. If after the flow process, one has to conduct intense purification techniques on the product, he or she has to use a plethora of solvent to get the product pure. One major source of impurity which requires intense purification to completely remove is from the catalyst in the reaction. A catalyst is anything which helps speed up a chemical reaction.
In this case, the element palladium is the catalyst used in our reaction. A way to avoid palladium from “sticking around” in your product after simple filtering techniques is to lock it up with another element. This not only makes the catalyst complex as a whole larger so it can’t get through the filtering material, but also it allows for the same palladium to be used again without being “swept away” in the product. An example of a common palladium catalyst is 10% palladium on carbon.
My project is focusing on a new palladium complex which was designed by a scientist who collaborates with Professor Vaccaro. I am conducting a specific type of chemical reaction which the final product is an example of an organic product which can be used in solar cells. The reaction is called a Sonogashira Coupling. I run the reaction with the palladium catalyst using a green solvent and conduct a simple filtering process when the reaction is complete. My reason for doing this is to measure the leaching of palladium in the final product. This leaching simply means the palladium is escaping from its complex which holds it in place.
With an increase in the leaching of palladium comes two things. Firstly, it means that the product is not as pure and therefore is not as efficient when it is used in organic solar cells. Secondly, it means that the ability of the catalyst to be effectively reused is reduced since it has lost some of the palladium. The goal of my project is to hopefully observe a decreased amount of palladium leaching as compared to traditional palladium catalysts and find the right reaction conditions for minimal leaching out of palladium.
I have been working for almost 3 weeks, and, while I am still working out some kinks, things are progressing nicely! I will keep you updated on my results. Pray for my work that it may be successful!
Ciao for now!
Chemistry Joke of the Blog
Want to hear a joke about Potassium? K.