State-of-the-art surface passivation of boron emitters using inline PECVD AlOx/SiNx stacks for industrial high-efficiency silicon wafer solar cells

Extremely low emitter saturation current density (J_0e) values of 6 and 45 fA/cm², respectively, are reported for 220 and 30 Ω/sq planar p⁺ boron emitters passivated by an AlO_x/SiN_x stack deposited in an industrial plasma-enhanced chemical vapor deposition (PECVD) reactor. The thermal activation of the AlO_x films is performed in a standard industrial fast firing furnace, making the developed passivation stack industrially viable. For textured p⁺ emitters the J_0e values are found to be 1.5 - 2 times higher compared to planar emitters. This excellent surface passivation is attributed to a high negative charge density of -(3-6)×10¹² cm^-2 in combination with a low interface defect density of ℒ10¹¹ eV^-1cm^-2. Assuming a short-circuit current density of 40 mA/cm² and the ideal diode law, the J_0e result for the 80 Ω/sq emitter represents a 1-sun open-circuit voltage limit of 736 mV at 25°C.