Exploring the efficiency limiting parameters trade-off at rear surface in passivated emitter rear contact (PERC) silicon solar cells

In recent years, there is a growing interest in reducing the various losses occurring at the rear surface of passivated emitter and rear contact (PERC) silicon solar cells through process optimization including chemical polishing, dielectric passivation and contact geometry etc. to realize the possible improvements in power conversion efficiency. In this contribution, a detailed investigation on recombination and resistive losses at rear surface of PERC solar cells using advanced imaging techniques for spatial distribution and allied characterization approaches are performed for better understanding of loss mechanisms and possible routes for their mitigation. Our analysis identifies that spreading resistance (R-spr) and reverse saturation current density due to first diode (J(01)) are the two key parameters in quantifying the efficiency improvement in PERC solar cells. For rear dielectric opening of 45 mu m, optimized circular contact geometry was found to exhibit lower R-spr, as well as J(01), when compared with the linear scheme. Our calculation also suggests an additional possible improvement of absolute 1.29% in power conversion efficiency through appropriate selection of starting wafer resistivity and improved passivation uniformity across the solar cell area.