Impedance spectroscopy characterization of c-Si solar cells with SiO_x/ Poly-Si rear passivating contacts

Impedance spectroscopy (IS) is a powerful characterization technique that is commonly applied to organic, perovskite, and thin-film solar cells. However, it has not been widely applied to solar cells based on crystalline silicon (c-Si), which is by far the most relevant commercial technology, and particularly not to modern, high-efficiency silicon devices. In this work, we demonstrate the application of the IS technique to a 21.25% efficient c-Si solar cell featuring SiO_x/poly-Si rear passivating contacts. This type of cell architecture is structurally similar to that of current high-efficiency industrial devices. The investigated cell was measured over a wide range of frequencies under illuminated open-circuit conditions and under different DC biases in darkness. The resistive and capacitive components associated with the p⁺–n junction and at n⁺-poly–n low–high junction, which cannot be resolved by standard DC measurements, are readily distinguished by the IS method. These parameters allowed for the determination of junction time constants and lifetimes. We find that the lifetimes derived from IS measurements performed under open-circuit illuminated conditions are in excellent agreement with the carrier recombination lifetime under illumination. Our findings demonstrate that IS is a promising technique to explore various dynamic properties of high-efficiency c-Si solar cells.