Properties of nanostructured pure β-In2S3 thin films prepared by sulfurization-assisted electrodeposition

Abstract

The development of pure-phase semi-conducting buffering materials as the substitution of conventional cadmium sulfide (CdS) is extremely important for the large-scale application of solar cells. Herein, we demonstrated a facile approach to deposit pure-phase indium sulfide (In2S3) thin films on the indium tin oxide (ITO) substrates by sulfurizing the co-electrodeposited In2S3 films. The effect of sulfurization temperatures (200–550 °C) on the surface morphologies, crystal structures, optical and electrical properties of In2S3 films was investigated. The results showed that the highly-oriented pure β-In2S3 thin films were obtained as the sulfurization temperature exceeded 250 °C. The obtained β-In2S3 films possessed a relatively ideal S/In atomic ratio and a continuous and densely packed surface feature. The optical band gaps of the β-In2S3 films have been determined in the range of 1.93 ± 0.01–2.06 ± 0.01 eV, which can be controlled by adjusting the sulfurization temperature. The electrical properties tests demonstrated that the pure β-In2S3 films obtained by sulfurizing at 550 °C exhibited the characteristic n-type semiconductors with a low electrical resistivity of 38.8 Ω cm, a carrier concentration of 3.8 × 1015 cm−3 and a carrier mobility of 42.3 cm2 V−1 s−1. This facile synthetic route is promising for the preparation of pure-phase In2S3 films, and then gives the guidance for future design and synthesis of other metal sulfide films for high-performance solar cells.