Origin of Screen-Printed Metal Contact Losses in Crystalline Silicon Solar Cells

Crystalline silicon solar cells are considered mainstream products in the photovoltaic market. To further improve their performance, it is important to reduce recombination at the contact between metal electrodes and the Si surface because the state of the metal-Si interface affects the saturation current density J(0.metal) and open-circuit voltage. Moreover, the large saturation current density strongly contributes to the performance degradation of the solar cells. Therefore, the interfacial structure formed by the metal electrodes and Si surface must be examined to minimize the J(0.metal) value. In this study, we investigated the formation mechanism of Ag crystallites on the surface of the Si emitter layer in screen-printed Ag paste. Interestingly, J(0.metal) was minimized by Ag epitaxial growth, which was verified using an atomic-scale approach. Furthermore, the effect of P doping on the Ag-Si interfacial structure reduced J(0.metal). Our study can provide insights into the origin of J(0.metal) for realizing high-performance solar cells.