Optimization of efficiency enhancement of TOPCon cells with boron selective emitter

Silicon solar cells with a tunnel oxide passivating contact (TOPCon) structure are the new mainstream products; however, emitter recombination has become the bottleneck for further improvement. The introduction of selective emitter (SE) technology becomes imperative to address this issue. In this study, the appropriate range of sheet resistance in the light-doped region (230-280 omega/sq)and the reasonable interval of the diffusion junction depth in the heavy-doped region (1.2-1.3 mu m) are presented. The selective emitter with a suitable doping distribution is realized using the mask and etch-back method. Compared to the homogeneous emitter with a sheet resistance of 150 omega/sq, J0e of 16 fA/cm2, and J0metal-front of 500 fA/cm2, the optimum selective emitter results in a J0e-light doping of 8 fA/cm2, J0e-heavy doping of 45 fA/cm2 and J0metal-front of 213 fA/cm2. Finally, the boron SETOPCon cell samples UOC (726.5 mV), FF (84.01%), and efficiency (25.51%) are obtained, compared with the TOPCon cell with homogeneous emitter Uoc (717.6 mV), FF (83.77%) and efficiency (25.17%) of the reference. In addition, the efficiency potential of the boron SE-TOPCon cell (26.02%) at the optimal process conditions is determined based on device simulations. This study provides a feasible technical path for mass-produced TOPCon cells to increase the efficiency to more than 26%.