Boron-doped polysilicon using spin-on doping for high-efficiency both-side passivating contact silicon solar cells

This study focuses on boron-doped p⁺polysilicon (poly-Si) passivating contacts using spin-on doping (SOD). Experimental conditions, including annealing conditions, SOD concentration, and poly-Si thickness, were controlled to improve passivation. Based on the analysis results, the passivation quality mainly changes with indiffusion and doping concentration, causing Auger recombination and field effects. Meanwhile, grain size also influences the passivation quality but showed marginal characteristics. Through further optimization using an etch back and diffusion barrier, the efficiency of the flat reference solar cell was improved to 17.5% with an open-circuit voltage of 695 mV using a p⁺ poly-Si contact emitter, the highest reported efficiency using SOD on saw-damage-etched surfaces. This study includes a detailed analysis of SOD p⁺ poly-Si and shows promising results with potential for application in tandem devices. Furthermore, the cell efficiency is expected to increase by controlling the doping profile and application of textured surfaces, selective emitters, and forming gas annealing (FGA).