Electronic Characteristics of Ultra‐Thin Passivation Layers for Silicon Photovoltaics

Abstract Surface passivating thin films are crucial for limiting the electrical losses during charge carrier collection in silicon photovoltaic devices. Certain dielectric coatings of more than 10 nm provide excellent surface passivation, and ultra‐thin (<2 nm) dielectric layers can serve as interlayers in passivating contacts. Here, ultra‐thin passivating films of SiO 2 , Al 2 O 3 , and HfO 2 are created via plasma‐enhanced atomic layer deposition and annealing. It is found that thin negatively charged HfO 2 layers exhibit excellent passivation properties—exceeding those of SiO 2 and Al 2 O 3 —with 0.9 nm HfO 2 annealed at 450 °C providing a surface recombination velocity of 18.6 cm s −1 . The passivation quality is dependent on annealing temperature and layer thickness, and optimum passivation is achieved with HfO 2 layers annealed at 450 °C measured to be 2.2–3.3 nm thick which give surface recombination velocities ≤2.5 cm s −1 and J 0 values of ≈14 fA cm −2 . The superior passivation quality of HfO 2 nanolayers makes them a promising candidate for future passivating contacts in high‐efficiency silicon solar cells.