Rheological properties and related screen-printing performance of low-temperature silver pastes for a-Si:H/c-Si heterojunction solar cells

Four different low-temperature silver pastes were utilized to make metal grids by screen printing for silicon heterojunction solar cells. The rheological behaviors of the low-temperature silver pastes were characterized by viscosity test, thixotropy test, oscillatory stress sweep test and creep-recovery test. The correlationship between the screen-printing performance and the rheological properties was investigated. It was found that the shear thinning behavior and the thixotropy behavior of the silver pastes were desirable for the screen-printing process. An obvious viscoelastic behavior of the silver paste was also helpful for improving its printability. Further, good recovery and low creep and recovery compliances could minimize the printing defects and the tendencies to bleed out during the screen-printing, and thus increase the aspect ratio of the printed grids.