Northwestern Uni boosts solar efficiency

Northwestern Uni has cracked a new anode coating strategy to get solar cells running more efficiently, according to the US educator, which will produce “cheaper, more manufacturable and more easily implemented solar cells”.

Here comes the science bit – concentrate. Greenbang will let Northwestern explain in its own words:

To date, the most successful type of plastic photovoltaic cell is called a “bulk-heterojunction cell.” This cell utilizes a layer consisting of a mixture of a semiconducting polymer (an electron donor) and a fullerene (an electron acceptor) sandwiched between two electrodes — one a transparent electrically conducting electrode (the anode, which is usually a tin-doped indium oxide) and a metal (the cathode), such as aluminum.

When light enters through the transparent conducting electrode and strikes the light-absorbing polymer layer, electricity flows due to formation of pairs of electrons and holes that separate and move to the cathode and anode, respectively. These moving charges are the electrical current (photocurrent) generated by the cell and are collected by the two electrodes, assuming that each type of charge can readily traverse the interface between the polymer-fullerene active layer and the correct electrode to carry away the charge — a significant challenge.

The Northwestern researchers employed a laser deposition technique that coats the anode with a very thin (5 to 10 nanometers thick) and smooth layer of nickel oxide. This material is an excellent conductor for extracting holes from the irradiated cell but, equally important, is an efficient “blocker” which prevents misdirected electrons from straying to the “wrong” electrode (the anode), which would compromise the cell energy conversion efficiency.

And in short, all this scientific talk translates to this: the researchers upped cell voltage by approximately 40 percent and the power conversion efficiency from approximately 3 to 4 percent to 5.2 to 5.6 percent.