Ultrasound assisted nickel plating and silicide contact formation for vertical multi-junction solar cells

• Ultrasound assisted nickel plating on the mirror polished silicon wafer with n+–p junctions has been made.
• Vacuum annealing at 500 °C ensured the transformation of the Ni/Si interface into a nickel monosilicide.
• X-ray diffractometry revealed that the annealed films have single phased NiSi polycrystalline structure.
• As scanning electron microscopy showed, the films were well adhered, smooth and nonporous.
• Dark current–voltage characteristics confirmed the creation of good nickel silicide ohmic contacts.

Vertical multijunction (VMJ) silicon solar cells (SC) are considered the most preferred among all known single-crystal ones for using in various photovoltaic systems under conditions of highly concentrated sunlight. The techniques of ultrasound assisted nickel plating (USNiP) of mirror polished silicon wafers and their subsequent vacuum annealing for VMJ SC ohmic contacts creating were tested by X-ray diffractometry, scanning electron microscopy and dark current–voltage characteristics. The feasibility of utilizing nickel electroplating in the sulfamate electrolyte for the NiSi ohmic contact made on the mirror polished silicon wafers with n+–p junctions on both sides have been experimentally confirmed. Ultrasound assistance of the nickel plating insured the enhancement of NiSi adhesion and improving the quality of the ohmic contacts.