Industrial implementation of bifacial PERC+ solar cells and modules: Present status and future opportunities

摘要

Since its first publication in 2015, the PERC+ cell concept, which is based on a passivated emitter and rear cell (PERC) design with a screen-printed Al finger grid on the rear, has been rapidly adopted by several solar cell manufacturers worldwide. The rapid industrial implementation of bifacial PERC+ cells is facilitated by the very similar process technology to that of mainstream monofacial PERC cells. Conversion efficiencies of industrial PERC+ solar cells of up to 22.1% (ISFH) with front-side illumination, and of 17.3% (LONGi) with rear-side illumination, have been reported. Meanwhile, four companies offer commercial bifacial PERC+ modules with a maximum rated power of around 300WP when illuminated from the front side only. These modules incorporate 60 PERC+ cells with four or five busbars, which are interconnected by conventional stringing and tabbing technology. The first small-scale outdoor installations have confirmed an increase in energy yield relative to monofacial PERC modules of between 13 and 22%. Two large-scale outdoor installations with peak capacities of 2MWp and 20MWp are currently under construction in Taiwan and China respectively. A novel bifacial PERC+ prototype module that uses Smart Wire Connection Technology (SWCT) is reported in this paper: a set of 18 halved PERC+ solar cells are interconnected by soldering 18 wires directly to the Ag front and Al rear fingers. The resulting prototype module exhibits independently confirmed front- and rear-side efficiencies of 19.8% and 16.4% respectively. Additionally, Meyer Burger has certified a full-size PERC+ SWCT module in accordance with the IEC 61215 norm, thereby demonstrating the long-term reliability of this novel module technology.