Mitigating edge recombination and moisture-induced degradation in HJT solar cells via Nafion-based edge passivation

Silicon heterojunction (HJT) solar cells are sensitive to recombination losses and moisture-induced degradation at mechanically exposed edges. In this study, an untreated 0 wt% control and Nafion solutions with concentrations of 3, 5, 7, and 10 wt% were evaluated on mechanically cut 4 cm × 4 cm HJT solar cells, corresponding to an active area of 16 cm 2 , four exposed edges, and a total exposed edge length of 16 cm. The devices were evaluated using illuminated J–V measurements, dark I–V characterization, damp heat testing at 85°C/85% RH, photoluminescence, X-ray photoelectron spectroscopy, and a calibrated analytical edge-recombination consistency assessment. The host-cell group before cutting exhibited average values of J sc  = 39.20 ± 0.05 mA/cm 2 , V oc  = 749.36 ± 1.00 mV, FF = 81.70 ± 0.30%, and PCE = 24.00 ± 0.15%. After mechanical cutting, the untreated cut-cell group exhibited J sc  = 38.20 ± 0.03 mA/cm 2 , V oc  = 722.00 ± 1.00 mV, FF = 78.39 ± 0.45%, and PCE = 21.62 ± 0.13%. The optimized 3 wt% Nafion-treated group achieved J sc  = 39.18 ± 0.05 mA/cm 2 , V oc  = 748.12 ± 1.32 mV, FF = 81.55 ± 0.32%, and PCE = 23.91 ± 0.15%. Based on the group-average values, the treatment recovered approximately 95.47% of the cutting-induced V oc loss and 96.22% of the PCE loss. The treated cells also retained higher illuminated J–V parameters during damp heat exposure, demonstrating that concentration-optimized Nafion edge passivation can improve both the efficiency and environmental stability of mechanically cut HJT solar cells.