Adhesion of reactive silver inks on indium tin oxide

Many emerging photovoltaic technologies, such as silicon heterojunction (SHJ) cells and perovskites, are temperature sensitive and are not compatible with the high sintering temperatures required for commercial screen-printed metallization pastes. Newer, low-temperature reactive silver inks exhibit good electrical conductivity and are compatible with temperature-sensitive substrates. However, preliminary investigations showed that the adhesion and reliability of these metallizations could vary dramatically with ink composition. This work evaluates the adhesion performance of printed reactive inks on indium tin oxide-coated SHJ cells to show that puckering phenomena originating from the porous nature of the printed reactive inks are responsible for lowering the as-printed adhesion strength. Adhesion performance was qualitatively determined using 180° peel test followed by optical imaging to quantify the amount of adhesive failure. Post-print scanning electron microscopy was used to observe the surface morphology. Diluting the reactive ink to reduce silver ion concentration decreased the observed puckering phenomenon and improved adhesion performance. This new understanding enables a more systematic design of reactive inks for novel photovoltaic applications.