Status of Al2O3/TiO2‐Based Antireflection and Surface Passivation for Silicon Solar Cells

Inhibiting charge recombination effectively by surface passivation is very important for high‐efficiency silicon solar cells. With the emergence of passivated emitter and rear cells (PERCs), which surpass conventional solar cells, the need for a novel passivation scheme is increasing. Passivation layer stacks using negatively charged Al 2 O 3 have been applied successfully to realize high‐efficiency PERC solar cells. Herein, the developments of surface passivation by Al 2 O 3 /TiO 2 ‐based layers are reviewed. The topics range from synthesis methods and optical properties as antireflection coatings to the electrical properties related to the material, interface, and passivation quality. Ultrathin Al 2 O 3 /TiO 2 ‐based layers generally feature a combination of field‐effect passivation by negative fixed charges, a low interface defect density, and adequate humidity stability. Among the various deposition methods, atomic layer deposition is focused on, which can form dual layers and nanolaminates. How the features of atomic‐layer‐deposited Al 2 O 3 /TiO 2 ‐based layers can be utilized for interface engineering and tailoring the properties of surface passivation schemes is discussed.