Avoidance of boron rich layer formation in the industrial boron spin-on dopant diffused n-type silicon solar cell without additional oxidation process

Abstract

In the present work, the properties of boron rich layer (BRL) formed in the boron spin-on dopant diffusion as well as the avoidance of BRL formation without additional oxidation process are studied. The boron concentration distributions characterized by SIMS exhibit the formation and avoidance of BRL with the variation of oxygen content in the boron diffusion process. The existence of BRL can degrade the minority carrier lifetime due to the enhancement of recombination as well as weaken the anti-reflection effect due to the unmatched refractive index of BRL and SiO2/SiNx stack layers. The decreased minority carrier lifetime together with the increased surface reflectance eventually deteriorates the electrical behavior of solar cell with a maximum power conversion efficiency loss of 0.55%. Significantly, the formation of BRL is found to be avoided due to the complete oxidation of excess elemental boron atoms when the oxygen content increases to 10%, contributing to the recovery of solar cells’ electrical performance with an average efficiency of 19.47%. The present work will be helpful to deepen the understanding of BRL and simplify the boron diffusion process for massive cell production.