Features of photoconversion in highly efficient silicon solar cells

The photoconversion efficiency $\eta$ in highly efficient silicon-based solar cells (SCs) is analyzed depending on the total surface-recombination rate $S_s$ on illuminated and rear surfaces. Solar cells based on silicon $p$–$n$ junctions and $\alpha$-Si:H or $\alpha$-SiC:H-Si heterojunctions (so-called HIT structures) are considered in a unified approach. It is shown that a common feature of these SCs is an increased open-circuit voltage $V_{\mathrm{oc}}$ associated with an additional contribution of the rear surface. Within an approach based on analysis of the physical features of photoconversion in SCs, taking into account the main recombination mechanisms, including Shockley–Read–Hall recombination, radiative recombination, surface recombination, recombination in the space-charge region, and band-to-band Auger recombination, expressions for the photoconversion efficiency of such SCs are obtained. The developed theory is compared with experiments, including those for SCs with record parameters, e.g., $\eta$ = 25% and 24.7% for SCs with a $p$–$n$ junction for HIT structures, respectively, under AM1.5 conditions. By comparing theory and experiment, the values of $S_s$ achieved as a result of recombination-loss minimization by various methods are determined. The results of calculations of the maximum possible value $\eta_{\mathrm{max}}$ in silicon SCs are compared with the data of other papers. Good agreement is observed.