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.