Insight into Al-Si interface of PERC by Kelvin probe force microscopy

Passivated emitter and rear cell (PERC) has the advantage of higher short circuit current and open circuit voltage, which are generally claimed to be related to the reduction of rear side recombination and the increase of rear surface reflection. However, few works have focused on exploring the internal conducting mechanism about it. Herein, the influence of PERC technique on improving the short circuit current is investigated by comparing a PERC with a single crystalline silicon (sc-Si) solar cell. The surface potential results measured by Kelvin probe force microscopy show a higher surface potential step at the Al-Si interface of PERC than that of sc-Si cell, indicating a severe energy band variation and a better carrier collecting ability of PERC. Moreover, by using advanced microstructure characterization techniques, the relationship among the surface potential step, morphology and element distribution is fully studied, which proposes a new viewpoint to explain the enhanced performance of PERC.