Investigation on Industrial Screen-Printed Aluminum Point Contact and Its Application in n-PERT Rear Junction Solar Cells

As compared with the traditional back surface field (BSF) solar cells, the n-type passivated emitter rear and totally diffused rear-junction (n-PERT-RJ) solar cells have much lower carrier recombination losses on their rear sides. In order to obtain more benefits (higher open-circuit voltages) from the currently passivated rear sides, the implementation of the point contact concept is an intuitive solution. In this article, we present industrial screen-printed point contacts that are metallized with aluminum (Al) pastes containing silicon additives (Si-add). To understand the impacts of the Si-add on the performance our n-PERT-RJ solar cells, the detailed loss analysis on the open-circuit voltage (VOC), short-circuit current density (JSC), and fill factor are performed separately. The effect of Si-add and pitch of laser contact openings (LCO) on the point contact characteristics are also investigated. In the last part, we introduce an innovative “point-line” contact concept on the rear side, which is composed of dot-shaped LCO and Al metal finger design, resulting in an n-PERT-RJ solar cell to reach VOC of 692 mV and peak efficiency of 22%. The 60% bifaciality of the device opens the way for an additional power output on module level, which further reduces the levelized cost of electricity. These features make the rear-side point contact design more flexible to be applied in industrial mass production.