CELLO: an advanced LBIC measurement technique for solar cell local characterization

An advanced light beam-induced current measurement for solar cell local characterization, called CELLO, has been developed and tested on mono- and multi-crystalline Si solar cells. A solar cell is illuminated at near 1.5 AM light intensity, and is additionally subjected to intensity modulated scanning local illumination by a focused IR-laser. The linear response (current or potential) of the solar cell is measured for various fixed global conditions (different preset voltage or current values) during scanning. A large number of independent data with high spatial resolution are obtained. Applying an advanced fitting procedure to these data yields a set of local parameters for each point on the solar cell. This gives information on the spatial distribution of the photo current, the series and shunt resistance, the lateral diffusion of minority carriers, the quality of the back surface field, and even allows the calculation of local IV curves. The theoretical and experimental approach to this technique will be discussed, and the applicability of this new solar cell characterization tool will be demonstrated.