Rapid and accurate characterization of silver-paste metallization on crystalline silicon solar cells by contact-end voltage measurement

Contact-end voltage measurement was applied to characterize the contact-formation process of silver paste metallization on p- and n-type crystalline silicon solar cells under different temperatures with well-designed fixtures and test patterns based on the circular transmission line model. The contact-end voltage values were found to be sensitive to sintering temperature, and the current density and contact end voltage curves of both contacts were linear, stating that the contacts were ohmic contacts. Their symbols on the n-type emitter reversed from negative to positive under the established connection mode, which indicated conductive-path changes manifested in the form of macroscopic electrical properties under insufficient, optimal, and over-fired conditions. We inferred that the conductive channel variations were mainly caused by the silver crystallites that precipitated on the emitter surface from the combination of the cross-sectional and interface morphology analyses. No similar phenomenon was observed on the p-type emitter for the few silver crystallites or silver-aluminum alloy without conductive-path alternation. Their values were much greater than those of the n-emitter, which agreed with the present industrial n-type cell characteristics. The measurement improved our understanding of the contact formation process, and can be used as a flexible approach for researchers to optimize the silver-paste formula and sintering processes for high-efficiency solar cells.