Over 700 mV Implied Voc on p-Type CZ Silicon Solar Cells with Double-Sided Laser Doping

Abstract

Efficiencies above 19% have been achieved by many PV manufacturers by applying different selective emitter technologies on p-type CZ silicon wafers with screen printed aluminium back-surface field which limits the voltage of the cell to below 640mV. In order to overcome this limit, in this paper, laser doping technology was applied into both surfaces of commercial grade p-type silicon wafer passivated with dielectric layer to form a pseudo solar cell structure with standard laser-doped selective emitter on the front and local back-surface field. This paper studies the passivation and thermal property of the dielectric layer. Post deposition annealing is investigated by measuring the minority carrier effective lifetime and implied Voc of the samples by photoluminescence imaging and photoconductance effective lifetime measurements. The influence of laser doping parameters on the implied Voc is also discussed in this work. As a result, implied Voc over 700mV was achieved on commercial grade p-type CZ silicon wafer after double sided laser doping process. This implied Voc is much higher, compared to the ones obtained by single-sided selective emitter structure.