Adaptation of the Industrial PERC Solar Cell Process Chain to Plated Ni/Cu/Ag Front Contact Metallization

Three approaches to close the efficiency gap between screen-printed Ag-paste and Ni/Cu/Ag-plated front contact metallization on industrial passivated emitter and rear cells (PERC) solar cells are presented in this paper. In the first approach, the POCl3 diffusion is adjusted to an emitter profile (reduced peak doping) for plated contacts. The second approach is to adapt the laser over doping (LOD) process of the phosphor silicate glass (PSG) to create the selective emitter to the properties of laser patterning and plating. In the third approach, we vary the process step order of front laser patterning and back side aluminum firing. The three approaches show very promising results. Efficiencies higher than 22% and open-circuit voltage VOC values of close to 680 mV are reached on a cell area of 251,99cm². Overall the values excel the reference values obtained with screen printing and firing of Ag-paste. For future developments, VOC values between 685 mV and 690 mV and efficiencies around 22.5% seem very likely.