Characterization and Analysis of Local Series Resistance on Quasi-Monocrystalline Solar Cells

Abstract

This work evaluates the application of Quasi-Monocrystalline silicon (QM-Si) wafers on the conventional structure of silicon solar cells textured by an alkaline solution to generate random pyramids. Although most areas of QM-Si wafers are <100> orientated by using a seeded-grown and directional-solidification process, there are still some none-<100> orientated areas randomly distributed on the wafers. These areas stay more planar, featuring worse reflectance and light trapping. Furthermore, series resistance (Rs) mapping on the final cells shows that these areas also have a higher local Rs. Our experiments and analysis show that the higher local Rs is mainly due to the poor Ag/Si contacts according to the results of our TLM measurement. Such higher local Rs values have led to only 76.3% fill factor and 17.1% efficiency performance of 500 cells on average. Further detailed investigations show that the local Rs, or local contact resistance, depends greatly on the surface roughness for screen printed cells, which implies that to take advantage of better quality of the QM-Si wafers, silver paste needs to be improved to form good contacts on both textured and planar silicon surface, when these wafers are textured with a random-pyramid alkaline process.