NanoLBIC Characterisation of Silicon Solar Cells Using a Laser Pick-up Unit

An innovative blue laser nano-LBIC system is designed and built, demonstrating capabilities as a versatile system for the optoelectronic characterisation of solar cells. A laser pick-up unit is used here to achieve a highly focused laser beam with a full width half maximum as low as 250 nm on the surface of a PERC solar cell. The quality of the resulting LBIC map is evaluated by cross-comparisons with optical micrographs on the same region of the PERC cell. LBIC imaging of laser doped emitters using 405 nm and 650 nm lasers reveals shallow locations of introduced structural defects, which are observed from the higher photocurrent loss in the image obtained by 405 nm photogeneration. A high-resolution map is generated to show current variation related to the surface texture of the cells, at a scale below one micron. Despite no image optimisation or filtering, the results indicate that the lateral resolution of our nano-LBIC system is comparable to that of complex confocal laser microscope-based systems. Our system can enable fast and point-of-manufacture visualisation of recombination inside photovoltaic devices with sub-micron spatial resolution without the need for complex optical or vacuum based systems.