Firing and contact resistivity of Ag₂O-aided Pb-free silver paste for crystalline silicon solar cells

The silver pastes containing Ag₂O powder, Ag powder, α-terpineol, ethyl-cellulose and Pb-free glass were synthesized for crystalline silicon (c-Si) solar cells. It was found that α-terpineol assisted the decomposition of Ag₂O powder and effectively lowered the decomposition temperature of Ag₂O. Ag nanoparticles were produced during the decomposition of Ag₂O, which helped to reduce the sintering temperature of the silver pastes. The Ag₂O-aided silver pastes were fired on polycrystalline silicon solar cells at various temperatures, and large plate-shaped Ag crystallites appeared at the interfaces between the sintered pastes and the emitter, which ensured a good electrical contact. The contact resistivity of Ag₂O-aided silver paste with an optimal ratio of Ag₂O to Ag was lower than that of the paste with pure Ag powder. The lowest contact resistivity of Ag₂O-aided Pb-free silver pastes sintered at 800°C was 0.029 Ω⋅cm², which was close to that of commercial silver paste that contained Pb-based glass (0.026 Ω⋅cm²). The experimental data demonstrated that the addition of Ag₂O reduced the contact resistance and promoted the sintering of Pb-free silver pastes, and Ag₂O-aided Pb-free silver paste could be a promising candidate used for front-contact electrode of c-Si solar cells.