Performance analysis of different dielectrics for solar cells with TOPCon structure

The performance of a TOPCon solar cell depends on the properties of the dielectric material through which tunneling takes place. Common dielectric material used with n-type Si wafer is SiO2 due to its excellent passivation property for n-Si interface. Required thickness of SiO2 is ≈1.5 nm, making its fabrication quite challenging. Moreover, recently p-type TOPCon solar cell has been proposed as an alternative to p-type PERC (p-PRC) structure. So, a dielectric material different from SiO2 may act as a better tunneling cum passivation layer for p-Si wafer. In this paper, various alternative tunneling/passivating dielectric layers like Si3N4, Al2O3, HfO2 and ZrO2 have been discussed. The cell performances as well as the critical dielectric thicknesses of all these materials have been simulated using the three-dimensional Sentaurus TCAD software. It has been found that the critical dielectric thickness for optimum cell performances depends strongly on the tunneling effective mass of the majority carriers, dielectric barrier at the dielectric/Si interface for the majority carriers and fixed charges in the dielectric. We have also used the simulation for an arbitrary generic dielectric and studied the dependence of its critical thickness (tcritical) on the three parameters mentioned above.