Abstract
Ag2Se, Ag-In-Se-based alloys and indium alloys are all frequently used in solar cells. This study experimentally examines the interfacial reactions in the In/Ag2Se couples and phase equilibria of the Ag-In-Se ternary system. A very unique alternating layer phenomenon is observed in the couple reacted at 450°C, 300°C and 140°C. An alternating phase formation with phase direction parallel to reaction zone/Ag2Se interface is observed. However, the phases formed are different and the alternating phases are In3Se4/liquid, In3Se4/AgIn2 and In3Se4(AgInSe2)/AgIn2, respectively. Ag whiskers as long as 10 cm are formed in the Ag-In-Se alloys, and striations and faceted microstructures are observed. Different Ag whiskers could have different growth directions, and the [200] preferred growth orientation has been determined. The compositional regime of Ag whisker growth in the Ag-In-Se ternary system is near the Ag-rich corner of about 15at.% Ag to 30at.%Ag, and is close to the compositional regime of the miscibility gap.