S tudy of surface cleaning before passivation and rear boron doping on high efficiency PERL solar cells

Two cleaning methods (SC-1,2 and SPM) before passivation and four boron sources (two kinds of spin-on boron dopant and two types of PECVD-deposited boron dopant) and three kinds of rear PECVD-deposited boron dopant layers (abbreviated as SiO2(B), SiNx(B) and a-Si(B)) are investigated. SPM was selected as the cost-effective cleaning method. PECVD-deposited p-type layer doped by diborane (B2H6) was chosen. SiO2(B) layers with different thicknesses were investigated and 100nm is suitable. Moreover, SiNx(B) layers with different refractive indices were studied and 2.1 is better. Finally, firing conditions were discussed for cells with a-Si(B). 19.8% efficiency was achieved with 400 degrees C, 1100mm/min firing.