Improvements in the efficiency of p-type bifacial Si solar cells with a rear Cu electrode using galvanic replacement reactions

A novel method for fabricating the base metal Cu in an air atmosphere was successfully developed based on thick film screen printing of Al pastes and galvanic replacement reactions. The first thick film screen printed Cu electrode with high conductivity (<10⁻⁶ Ω-cm), which is comparable to thick film Ag electrode, was successfully made in air firing instead of reducing atmosphere firing. In this study, a high-efficiency p-type bifacial PERC solar cells with an industrial typical PERC process flow is introduced, used to apply a screen-printed aluminum finger grid on the rear side of an electrode, instead of a full-area aluminum layer. A novel copper (Cu) technique is used to fabricate the rear Cu electrodes that are substituted for rear Al electrodes in p-type PERC c-Si solar cells. The F.F. and efficiency of the p-PERT solar cell with the novel rear copper electrode can be remarkably improved by this method. The maximum efficiency of the p-type bifacial single crystalline solar cells obtained with this process was 22% for the front Ag side and 19.7% for the rear Cu side illumination under standard testing conditions (STC). The ratio between front and rear side performance was over 89% for all of the solar cells.