Korean Journal of Materials Research ISSN:1225-0562(Print) 2287-7258(Online) 한국재료학회지

Silicon heterojunction solar cells can achieve high conversion efficiency with a simple structure. In this study, we investigate the passivation characteristics of VO_x thin films as a hole-selective contact layer using ALD (atomic layer deposition). Passivation characteristics improve with iV_oc (implied open-circuit voltage) of 662 mV and minority carrier lifetime of 73.9 μs after post-deposition annealing (PDA) at 100 °C. The improved values are mainly attributed to a decrease in carbon during the VO_x thin film process after PDA. However, once it is annealed at temperatures above 250 °C the properties are rapidly degraded. X-ray photoelectron spectroscopy is used to analyze the chemical states of the VO_x thin film. As the annealing temperature increases, it shows more formation of SiO_x at the interface increases. The ratio of V⁵⁺ to V4+, which is the oxidation states of vanadium oxide thin films, are 6:4 for both as-deposition and annealing at 100 °C, and 5:5 for annealing at 300 °C. The lower the carbon content of the ALD VO_x film and the higher the V⁵⁺ ratio, the better the passivation characteristics.