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

Abstract

In this investigation, Al2O3/TiO2 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 TiO2 deposition. Aluminum sulfate and sodium bicarbonate were used for Al2O3 deposition. The concentration of the sodium bicarbonate and boric acid in the deposition solution controls the rate of deposition of Al2O3 and TiO2 films. Under optimal conditions, the average refractive index of liquid phase deposited Al2O3 and liquid phase deposited TiO2 films was 1.58 and 1.76, respectively. The average reflectance was 3.3% at wavelengths from 400 to 800nm for liquid phase deposited Al2O3 and liquid phase deposited TiO2 film thicknesses of 99 and 89nm, 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.