Build Your Own Dye-Sensitized Solar Cell
In 1991 Brian O’Regan and Michael Gratzel published a paper titled “A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films.” This paper is the foundation for an entire branch of solar energy conversion research known as dye-sensitized solar cells (DSSC).
The basic operation of a DSSC is summarized in the schematic below. In roughly a stepwise manner:
- Light (hν) hits a light-absorbing molecule ( chromophore, C), causing it to enter an energetically excited state (C*).
- The excited chromophore injects an electron (e-) into the anode.
- The iodine (I-) in solution donates an e- to the previously oxidized C and combines with I2 to become I3- .
- The high energy e- from step 2 enters the external circuit where it can be used to perform work on a load (e.g., charge a battery, run a fan).
- The low energy e- then continues to the cathode where it catalytically reduces I3- to I- and completes the circuit.
The 1991 Gratzel paper was groundbreaking because it introduced the use of a high surface area TiO2 semiconductor electrode as the anode material. With a higher surface area, more chromophore can be loaded on the surface to increase light absorption and thus can generate more photocurrent. Using this basic architecture – with variations to its components – has allowed us to realizef efficiencies greater than 10% in the lab. Companies like Dysol and others are currently commercializing this technology.
As well as being groundbreaking the DSSC is relatively simple with four basic components: an anode acceptor material, a chromophore, a reversibly redox active electrolyte and a cathode material that can catalytically reduce the electrolyte. Given the availability of these components, Greg P. Smestad and Michael Gratzel later published a procedure in the Journal of Chemical Education that allows just about anyone to create their own DSSC. The Institute of Chemical Education (ICE), based out of the University of Wisconsin, has taken the educational utility of this paper one step further and created a $45 Nanocrystalline Solar Cell Kit. The components of this kit can be seen in the figure below. It consists of 1) 10 x SnO2 conductive glass slides, 2) 15 mL of I-/I2 ethylene glycol solution, 3) 25 g TiO2 powder, 4) a soft graphite pencil, 5) 10 x binder clips and 6) a variable resistor.
All that you need in addition to the kit is an oven/hot plate that can sinter the film at 450°C; a dye that can be easily obtained from raspberries, blue berries, black berries or other fruits; and a mortar/pestle to grind up the TiO2 while adding acetic acid. The assembled solar cell is shown in the top left of the image. From the kit you can make up to five solar cells at a time and, because many of the components are reusable, the process can be repeated several times. The ICE manual that comes with the kit provides clear instructions for assembling, characterizing and cleaning the devices. It also includes background information, visual aids, graphing paper, teaching suggestions and other useful tips/hints for trouble-shooting the devices.
While DSSCs are currently being studied by graduate students and researchers all over the world, the concepts and components of these devices are so simple that they can be used for teaching activities in middle schools and undergraduate chemistry labs. In fact, last week I had the pleasure of demonstrating this kit/exercise for local high school and middle school science teachers through a program sponsored by the University of North Carolina at Chapel Hill’s Institute for the Environment. 
I have been involved with solar cell technology as a researcher for several years, and I can say without a hesitation that I was blown away by how user-friendly the kits are – especially given the high level of science involved. For example, you can construct the circuit in the image to the right (top) using two $10 multimeters from Radio Shack, the variable resistor that comes with the kit and your fully assembled cell. While shining light on the cell and changing the variable resistor, the relationship between the current (I) and voltage (V) can be documented (The graph of voltage versus current is a common sight to anyone that has studied solar cells.) An incredible amount of information can be obtained from these I/V curves, like open circuit voltage (Voc), short circuit current (Isc), power maximum (Pmax), fill factor (FF), shunt resistance (RSH) and series resistance (RS). Also, if you know the power of incident light (Pinc = 800-1000 W/m2, for daytime sunlight) you can calculate the device efficiency (h) by dividing Pmax by Pinc.
The DSSC kits are exciting because of the various opportunities they provide to teach high level scientific concepts and troubleshooting through simple hands on activities. Middle school students can compare different dyes and their effect on the devices’ efficiencies/current/voltages. Undergraduate inorganic chemistry students can synthesize and compare various dyes. These exercises can also bring together concepts in biology, chemistry, and physics classes. For example, students can prepare chlorophyll dye through enzymatic reactions in a biology lab, fabricate and load the dye on the TiO2 films in chemistry class, and then do the I/V characterization or measure the parallel versus series currents of several devices in physics class.
Irrelevent though it might be, I had tutorials with Brian. He was an absolute legend.
This is really cool. I did my undergrad and grad studies at EPFL, the Swiss institute where Grätzel works. I remember the day when I first visited EPFL as a prospective student, we had people from the Grätzel lab teaching us how to extract dyes from raspberries and build DSSCs. That was an awesome experiment for the high-school student I was at the time (I also won the chocolate box offered to the owner of the ‘most efficient’ DSSC).
Great tutorial! Thanks for sharing this interesting idea to us. I would love to do this at home to also experience building my own solar cell.
Dear Sir,
Greetings!
I am G.Paramaguru, Research Scholar, School of Chemistry, Bharathidasan University,Tiruchirappalli,India.
My area of research is synthesizing organic sensitizers for dye sensitized solar cells.
I found this article very useful for my research.
Since in my University there is no facility for solar cell research.
Can I do the efficiency for my dyes using this kit. If it so please guide me how to get this kit, How much it cost for an overall setup including multimeter and other accesories.
I kindly request you to help me which will be useful for my research.
Thanking You
Yours Sincerely
G.Paramaguru
G. Paramaguru,
Comparing your dye to a standard dye like N3 or N719 using this type of DSSC preparation and characterization would give you the general trends in device efficiency, Voc, Jsc, etc. The total cost for the kit and multimeters is about $70 (shipping in the US). The links to purchase the kit is included in the above post. However, I can say with relatively high certainty that those results would not get through the peer review process necessary for publication. An actual solar testing station has many necessary advantages over this type of measurement. 1) A standardized AM1.5 solar spectrum light source with a reference cell. 2) Wavelength dependent IPCE and APCE measurements. 3) Accurate I/V curves without losses associated with variable resistors. 4) Above all else is the reproducibility of the measurement.
If you don’t have the $50,000 (USD) to spend on a solar testing station but are still interested in getting publishable DSSC measurements for your dyes I would recommend finding a collaborator, either in India or elsewhere, that has a testing station. If they are interested it should be relatively easy to incorporate your dye into devices and test them. Before you mail them off, the above DSSC kit might be a means for you to test which ones are worth pursuing further. Even then I would make several of the devices to make sure your device failure is not because of the dye. DSSCs have a lot of “moving” parts. All of which can result in poor device performance.
Let me know if you have any more questions.
Kenneth Hanson
vastib@chemistry-blog.com
Dear Sir,
Thanks for your valuable suggestions in determining DSSC efficiency.
I will try to get colloboration in India for my studies.
I understood that this kit will give me some basic ideas and experience.
Whether now you are working in Dye sensitized solar cell?
Thanking You
Yours Sincerely
G.Paramaguru
G. Paramaguru,
I am working on research related to DSSCs but much more on the spectroscopy end looking at electron transfer events at the interface.
Kenneth Hanson
Dear Sir,
Greetings!
I am searching for collaborations to test efficiencies for my compounds.
I need your contact often so that I can improve my area of subject.
I kindly request you to give your e mail id.
Thanking You
Yours Sincerely
G.Paramaguru
Dear Sir,
We are at the very start of a project with the end goal of manufacturing DSSCs as a cottage industry for village lighting.
We have set up a team of 5 engineers and 2 chemists to do some basic investigations. The major task is to make suitable dyes locally but ofcourse we do not intend to discover the wheel.
Your kit can be a good start to learn the basics. How can we buy these kits? How else can you help us? We will be sharing our knowledge with all those who will help our project to get off the ground.
I was in the promotional team for chemistry at the Rijksuniversiteit Groningen. Our faculty actually owns a large truck (www.rug.nl/discovery) with which we visited schools throughout the Netherlands and further to give 45 minutes seminars. A lot of schools requested (and still do) this seminar, and sometimes I would have 8 classes of high school youngsters making these. I bet half of the Dutch youth have made a DSSC by themselves by now
. Even had our prime-minister making one (only 0.018 V 
We always used hibiscus tea as a dye though.
Great post! You explained the workings of the solar cell a lot better than I did to those kids!
In case anyone is interested or knows someone that might be, Alexander Ovsov has translated the article into Romanian.
http://webhostinggeeks.com/science/build-your-rm
Thanks Alex!
Solar power is really the only way to go. We all need to do our part to spread the word. It’s just about getting the word out that solar and going green takes “just about the same effort”.
Does anyone know how long the solutions (titanium dioxide, iodine) will last?
The only thing too expensive for us to buy for home is accurate scales so ingredients have to be weighed at school,
In spite of our school’s apathy for science, my son won 2 medals in physics labs at regional Olympiad last year. There is no team this year so he is competing in regional fair. Fortunately he has an idea to test that I have not already seen on the Internet!
This tutorial is amazing, thank you very much about this information. Keep up the good work!