Design and characterization of an adhesion strength tester for evaluating metal contacts on silicon solar cells

Strong contact adhesion is an important requirement for durable, manufacturable solar cells. Advanced contacting technologies require new methods to measure adhesion. We describe a scratch test for measuring contact adhesion that involves scanning a weighted stylus across the cell while measuring the horizontal force F_D required to dislodge the contacts. F_D is characteristic of the adhesive bond but independent of the contact height, stylus weight and scan speed. We observe that contact peeling depends also on the tensile strength of the metal finger. The tests provide a valuable way to assess and optimize the adhesion of metal contacts.