Properties of double-layer Al2O3/TiO2 antireflection coatings by liquid phase deposition

Abstract In this investigation, Al 2 O 3 /TiO 2 double-layer antireflection coatings were deposited on polished silicon substrate by using liquid phase deposition. The deposition solution of ammonium hexafluoro-titanate and boric acid was used for TiO 2 deposition. Aluminum sulfate and sodium bicarbonate were used for Al 2 O 3 deposition. The concentration of the sodium bicarbonate and boric acid in the deposition solution controls the rate of deposition of Al 2 O 3 and TiO 2 films. Under optimal conditions, the average refractive index of liquid phase deposited Al 2 O 3 and liquid phase deposited TiO 2 films was 1.58 and 1.76, respectively. The average reflectance was 3.3% at wavelengths from 400 to 800 nm for liquid phase deposited Al 2 O 3 and liquid phase deposited TiO 2 film thicknesses of 99 and 89 nm, respectively. This antireflective property was comparable to other vacuum deposition methods, such as plasma-enhanced chemical vapor deposition and sputtering; thus, the liquid phase deposition of antireflection coatings was highly favorable for silicon-based solar cells.