Method for optimizing the parameters of heterojunction photovoltaic cells based on crystalline silicon

An approach is proposed to calculate the optimal parameters of silicon-based heterojunction solar cells whose key feature is a low rate of recombination processes in comparison with direct-gap semiconductors. It is shown that at relatively low majority-carrier concentrations ($N_d$ $\sim$ 10$^{15}$ cm$^{-3}$), the excess carrier concentration can be comparable to or higher than $N_d$. In this case, the efficiency $\eta$ is independent of $N_d$. At higher $N_d$, the dependence $\eta(N_d)$ is defined by two opposite trends. One of them promotes an increase in $\eta$ with $N_d$, and the other associated with Auger recombination leads to a decrease in $\eta$. The optimum value $N_{d}\approx$ 2 $\cdot$ 10$^{16}$ cm$^{-3}$ at which $\eta$ of such a cell is maximum is determined. It is shown that maximum $\eta$ is 1.5–2% higher than $\eta$ at 10$^{15}$ cm$^{-3}$.