Silver-lean metallization and hybrid contacts via plating on screen-printed metal for silicon solar cells manufacturing

Abstract

As PV manufacturing heads towards the multi-TW scale, it is required to carefully evaluate a wide range of concepts including not only efficiency and cost but also material consumption to ensure sustainable manufacturing of PV technologies. The rapid growth of PV could significantly increase the demand for several materials required in solar cells such as silver, aluminium, copper and even silicon, thereby causing dramatic price fluctuations. Furthermore, the PV manufacturing capacity would be at risk of being limited by the supply of some scarce metals, e.g. with current industrial implementations – screen printing (SP) metallization, the capacities of PERC and TOPCon could be capped at 377 GW and 227 GW with 20% of global silver supply available to the PV industry. In addition, PV systems have ~25–30 years lifespan to ensure low LCOE and emissions. Recycling alone will not provide an immediate solution to overcome the limitation of material consumption in the exponentially growing PV market. It is expected that the Ag usage needs to be reduced to no more than 5 mg/W or even 2 mg/W for all solar cell technologies to allow a multi-TW manufacturing scale without depleting the global silver supply. Therefore, further advancements in metallization technologies are critically and urgently required to significantly reduce the silver consumption of current screen-printed contacts in industrial silicon solar cells. This paper firstly presents a roadmap towards the 5 mg/W and 2 mg/W silver consumption targets with various metallization technologies and screen-printing designs. Subsequently, a hybrid plating on screen-printed metallization design was proposed to improve the performance and reduce the silver consumption of screen-printed contacts. The experimental results have demonstrated up to 1.08%_abs improvements in fill factor and 0.3%_abs gains in cell efficiency. In addition, up to 40%_rel reductions in finger silver consumption have been achieved without any sacrifices in the electrical conductivity of such hybrid screen-printed and plated fingers. This work proposes not only a roadmap but also a promising approach to significantly reduce the Ag demand and benefit sustainable production of industrial screen-printed silicon solar cells in the TW era.