Investigation of methods for adhesion characterization of evaporated aluminum layers

This paper analyzes methods for measuring the adhesion quality of aluminum (Al) rear metallization deposited by means of physical vapour deposition (PVD) on rear passivation layers of passivated emitter and rear silicon solar cells (PERC). Since the standard test procedures for adhesion testing of solar cells cannot be applied, a peel-test and a direct-pull method are introduced and used for measuring the adhesion of test samples; criteria for adhesion evaluation are developed and applied. The results of adhesion tests are compared and are in good general agreement. The applicability of the two methods is discussed and it is found that the peel-test shows more reliable results whereas the direct-pull method is easier in preparation. Moreover, the results of the test samples show sufficiently good adhesion quality for the PVD rear metallization of PERC solar cells.