Quantifying Junction/Edge Defect Density of Crystalline Silicon Solar Cells Enabled by Depth‐Resolved Transient Photovoltage Decay

In the pursuit of higher efficiency for crystalline silicon (c-Si) solar cells, understanding carrier recombination dynamics is essential. While transient photovoltage (TPV) spectroscopy provides excellent temporal resolution for probing recombination, it conventionally offers no spatial resolution to analyze local behavior. Herein, we report a depth-resolved TPV system that enables localized analysis of carrier dynamics by tuning the excitation wavelength to control light penetration depth. The technique was used to explore internal carrier recombination in silicon heterojunction (SHJ) and tunnel oxide passivated contact (TOPCon) solar cells. Interestingly, SHJ cells exhibit low and symmetric internal recombination owing to effective passivation by intrinsic hydrogenated amorphous silicon layers on both sides. In contrast, TOPCon cells display higher recombination at the front surface due to insufficient surface passivation. Furthermore, edge-resolved measurements reveal that subsurface defects contribute significantly to edge recombination, particularly in SHJ solar cells. Finally, by correlating the TPV decay lifetime constant with the defect-state density, we obtained a layer-resolved quantitative estimate of the defect distribution within the solar cell. In addition, the transient monitoring of carrier diffusion and recombination was validated through photovoltage-decay simulations. Our findings elucidate the asymmetric recombination behavior and establish depth‑resolved TPV as a powerful diagnostic tool for advanced photovoltaics.