Optimization of rear-side passivation for enhancing the performance of bifacial PERC+ solar cells

For the passivated emitter and rear cells with bifacial power generation (known as PERC+), the rear-side efficiency is very important and critical. In this work, the influence of SiNx and SiOxNy as rear-side passivation films on the performance of PERC + cells was investigated. It was found that the SiNx film is better in terms of passivation performance and resistance to aluminum paste erosion, while the SiOxNy film exhibits a better optical performance. To synthesize the benefits of SiNx and SiOxNy, the multi-layer SiNx/SiOxNy/SiNx stacks were designed with the Wafer ray tracer system. The front-side efficiency of the optimized cells with SiNx/SiOxNy/SiNx passivation stacks was increased by 0.09 % as compared with the cells passivated with a single SiNx film of 80 nm in thickness. Moreover, in contrast with the cells with a rear-side SiNx film of 150 nm in thickness and the basically same front-side efficiency, the rear-side efficiency and bifaciality were increased by 1.55 % and 6.79 %, respectively.