Low-Temperature Drop-on-Demand Reactive Silver Inks for Solar Cell Front-Grid Metallization

Formation of high-conductivity metal contacts at low temperatures expands optoelectronic device opportunities to include thermally sensitive layers, while reducing expended thermal budget for fabrication. This includes high-efficiency silicon heterojunction solar cells with intrinsic amorphous silicon layers. Efficiencies of these cells are limited by series resistance; the primary cause of this is the relatively high resistivity of the low-Temperature silver paste used to form front-grid metallization. In this paper, we report the formation of highly conductive features by drop-on-demand printing of reactive silver ink (RSI) at a low temperature of 78 °C, resulting in media resistivities of 3-5 μΩ·cm. When used as a front grid on a silicon heterojunction solar cell, RSI fingers give cell series resistance of 1.8 Ω·cm² (without optimization of the process), which is impressively close to 1.1 Ω·cm² for our commercially available screen-printed low-Temperature silver paste metallization. We present here the promising first results of RSI as metallic finger for photovoltaics, which upon optimization of design parameters has the potential to outperform the screen-printed low-Temperature silver paste counterpart.