Measuring I-V curve allows determining the operating parameters of a solar cell, especially the conversion efficiency. The problem is that the sole I-V curve (static characterization of the device) is unable of giving us useful information about the causes reducing functionality. The total device resistance is related to the derivative of the I-V curve, and this resistance has in principle more than just one contribution. For instance resistance placed in series (not directly related to the photovoltaic action) might have a significant detrimental impact. As drawn in the next figure increasing the series resistance has the effect of destroying the solar cell performance.
This slideshow requires JavaScript.
Device modeling enters the scene aiming at decomposing separate contributions to the total resistance. The upper picture allows distinguishing contributions to the series resistance coming from transport and interfacial mechanisms. This is an example of device modeling applicable to dye-sensitized solar cells at forward bias. The extraction of each contribution to the total resistance is experimentally feasible by using impedance spectroscopy techniques. We see then that the interplay between measuring and modeling might imply substantial operation improvement by identifying limiting processes, in this particular case limiting transport processes.
Advertisement
