Tailoring interdigitated back contacts for high-performance bifacial silicon solar cells

Photovoltaic (PV) cells have become one of the most promising renewable energy technologies. To make PV cells more competitive with incumbent technologies, higher power output densities are needed. One promising approach is to add bifaciality to existing monofacial PV devices, allowing more output power from the additional reflection of sunlight from the ground (albedo a). For example, bifaciality can be added to Silicon Heterojunction (SHJ) solar cells with Interdigitated Back Contacts (IBCs) by opening up the gaps between the back metal contacts, but the optimum gap (w) that maximizes the power output is unknown. In this paper, we show that the optimum gap [w = 1 - (1 + alpha)(alpha(alpha + c)(-1/2)] maximizes the IBC-SHJ bifacial power output [P proportional to (alpha)(1 - 2 root a/c)], where c is the ratio of output power density to power loss due to shadowing and Joule heating, The results are validated by self-consistent finite-element device modeling. For a typical alpha = 0.3, an optimized bifacial IBC SHJ cell will produce 17% more power output than state-of-the-art monofacial IBC SHJ cells. The results encourage development of bifacial IBC solar cells as a next generation PV technology. Published under license by AIP Publishing.