Light‐enhanced surface passivation of TiO₂‐coated silicon

Titanium dioxide is shown to afford good passivation to non‐diffused silicon surfaces and boron‐diffused surfaces after a low‐temperature anneal. The passivation most likely owes to the significant levels of negative charge instilled in the films, and passivation is enhanced by illumination—advantageous for solar cells—indicating that a titanium dioxide photoreaction is at least partly responsible for the low surface recombination. We demonstrate a surface recombination velocity of less than 30 cm/s, on a 5‐Ω cm n‐type silicon, and an emitter saturation current density of 90 fA/cm 2 on a 200‐Ω/sq boron diffusion. If these titanium dioxide passivated boron‐diffused surfaces were employed in a crystalline silicon solar cell, an open‐circuit voltage as high as 685 mV could be achieved. Given that TiO 2 has a high refractive index and was deposited with atmospheric pressure chemical vapour deposition, an inexpensive technique, it has the potential as a passivating antireflection coating for industrial boron‐diffused silicon solar cells.