Effect of the Ti/Si ratio of spin coating solutions on surface passivation of crystalline silicon by TiO ^sub x^ –SiO ^sub x^ composite films

Passivation films or antireflection coatings are generally prepared using costly vacuum or high-temperature processes. Thus, we report the preparation of TiO x –SiO x composite films by novel spin coatable solutions for the synthesis of low-cost passivation coating materials. The desired films were formed by varying the mixing ratios of TiO x and SiO x , and the resulting films exhibited excellent surface passivation properties. For the p-type wafer, an optimal effective surface recombination velocity (S eff) of 93 cm/s was achieved at TiOx: SiOx= 6:4, while a surface recombination current density (J 0s) of 195 fA/cm2 was obtained. In contrast, for the n-type wafer, an S eff of 27 cm/s and a J 0s of 38 fA/cm2 were achieved at TiOx : SiOx= 8:2. This excellent surface passivation effect could be attributed to the low interface state density and high positive fixed charge density. Furthermore, the thickness of the interfacial SiO x layer was determined to be important for obtaining the desired surface passivation effect.