Two-dimensional Janus 1T-ScTeX (X = Cl, Br, I) monolayers for high-efficiency energy conversion applications

Abstract

In this paper, the properties of Janus 1T-ScTeX (X = Cl, Br, I) monolayers have been thoroughly examined based on first-principles calculations. The results confirm that these materials are stable and highly flexible. Each monolayer exhibits an indirect bandgap semiconductor nature and its bandgap values and edge positions can be effectively controlled by biaxial strain. Janus 1T-ScTeX monolayers exhibit significant out-of-plane piezoelectricity, with 1T-ScTeCl showing the highest out-of-plane piezoelectricity coefficient (3.90 pm V⁻¹) and notable strain sensitivity. 1T-ScTeBr has an electron mobility of up to 8844.50 cm² V⁻¹ s⁻¹ in the y-direction. The materials display a wide range of high-efficiency light absorption characteristics on the order of 10⁵ cm⁻¹ in the infrared to ultraviolet region. The combination of suitable band edge positions, outstanding out-of-plane piezoelectric effects, high carrier mobility, and efficient light absorption gives 1T-ScTeX monolayers excellent potential for photocatalytic water splitting. Among them, 1T-ScTeI becomes the optimal candidate material due to its ability to simultaneously meet the redox potential requirements for water splitting over a wide pH range. Given these properties, Janus 1T-ScTeX monolayers show promising applications in flexible electronics, piezoelectric transducers, and photocatalysis.