Figure10 (a) The light I-V curves and (b) EQE spectra of the SHJ solar cells with IHfO:H (Cell 1) or ITO (Cell 2) as the front-side TCO under optimal conditions.

Finally, a bifacial SHJ solar cell with an area of 274.15 cm² was fabricated using IHfO:H film deposited with a H₂ concentration of 0.8 % as the front-side TCO (Cell Ⅰ). And a control bifacial SHJ cell with ITO on both sides (Cell Ⅱ) was also assembled as a comparison. Post annealing was carried out in air under a temperature of 200 °C for 20 minutes for the whole devices. The light I-V and EQE curves of Cell Ⅰ and Cell Ⅱ are shown in Figure 10. The two solar cells do not show significant differences in open circuit voltage (V_oc) or FF. The improvement of 0.3 % in efficiency (Eff) for Cell Ⅰ (25.03 %) compared with Cell II (24.73 %) is mainly brought by the increase of 0.84 mA/cm² in J_sc. The significant increase in EQE in the long wavelength range (>850 nm) indicates reduced FCA for Cell I using IHfO:H compared with Cell I using ITO as the front-side TCO layer. The excellent device performance indicates that the IHfO:H films prepared by RPD have the great application potential in high efficiency SHJ solar cells.