Photovoltaic and Optoelectronic Devices Group, Department of Physics, Universitat Jaume I, ES-12071 Castelló, Spain
It is commonly accepted that modeling an electrical system mainly consists of establishing a set of structural relations between suitable parameters which represent its electrical response. But in many cases, the role of instrumentation in the process of model construction is not explicitly acknowledged. Measurements are always a part of the model-creating process as modeling and measuring become parallel activities in practical terms. In the specific case of photovoltaic devices the sole current-voltage response contains poor information about the kinetic mechanisms limiting the solar cell performance. Impedance spectroscopy goes beyond static measurements by applying a small oscillating perturbation to a given steady state. Because the frequency of the oscillation is changed during the experiment separate structural parts of the device are able to electrically respond. This is why impedance can be regarded as a spectroscopy. Knowledge about functional materials, device structure, and impedance response should be combined to devise an electrical circuit which represents the electrical equivalent of the device response (more info about impedance courses by the group at http://www.hopv.org/ISSCHOOL11/ ).
