On the limiting efficiency for silicon heterojunction solar cells

Silicon heterojunction (SHJ) solar cell, as one of the promising technologies for next-generation passivating contact solar cells, employs an undiffused and n-type mono-crystalline silicon (c-Si) substrate and two amorphous-silicon-based selective contacts with opposite polarities. In this work, a numerical model based on Richter's theory has been developed to simulate the performances of a 25.11 % efficiency SHJ solar cell obtained recently. Analyses on series resistivity (Rs) explicit that the upper bound for the sum of contact resistivities for p-type (ρc,p) and n-type (ρc,n) contacts is 0.073 Ω cm2. With the updated contact resistivities, the theoretical limiting efficiency estimated by Brendel's formulation is therefore 28.5 % for SHJ solar cells, which is comparable to 28.7 % for bi-facial tunneling-oxide passivating contact (TOPCon) solar cells. A hybrid structure consisting of p-type contact from SHJ and n-type contact from TOPCon is feasible to reach 28.9 % limiting efficiency in principle, showing potential of solar cells with hybrid structures.