Dye-sensitized (Graetzel) solar cells have been in the spot of many minds since they were first created in early ’90s by Michael Graetzel, from EPFL, Switzerland. Until now, dye-sensitized solar cells only proved to be cheap, but also inefficient. New technologies are expected to improve their performances.
Graetzel cells work on the same principle photosynthesis does. They are made of a porous layer of nanoparticles of titanium dioxide (white), covered with a molecular dye (of various colors) that absorbs sunlight, just like chlorophyll in green leaves. The whole thing is them immersed in an electrolyte, and a platinum-based catalyst completes the cell.
Two electrodes are placed on either side of the electrolyte, with sunlight passing through and withdrawing electrons from the titanium dioxide, a semiconductor at the bottom of the cell. These electrons travel through a wire from the anode to the cathode, creating an electrical current. In this way, energy from the sun is converted into electricity.
Everything sounds just fine in theory, but practice proves dye cells can’t be made effective so easily. Professor Benoi®t Marsan and his team at the Université du Québec i Montréal (UQAM) Chemistry Department, devised a series of improvements to the Graetzel cell that would decrease the manufacturing cost, increase its efficiency and physical resistance.
First, prof. Marsan developed a new electrolyte. Unlike the old one, that was extremely corrosive, making the cell less durable, this new one features entirely new designed molecules in high concentration. The new electrolyte is in gel form, transparent and non-corrosive. It can increase the cell’s voltage, which can currently deliver only 0.7 V.
The platinum covering the cathode has been replaced with cobalt sulphide, which is a lot cheaper, more efficient, stable, and easy to manufacture.
Professor Marsan has been helped by his colleague from the Chemistry Department, prof. Livain Breau.