Non-toxically enhanced sulfur reaction for formation of chalcogenide thin films using a thermal cracker

Sulfur-based metal chalcogenide films have been widely used for high-performance optoelectronic devices due to their attractive optical and electrical properties. Although typical approaches to the chemical deposition of chalcogenide films have some advantages such as large-area coverage and high thickness controllability, these processes require highly toxic and expensive hydrogenated materials. Here, we demonstrate an enhanced sulfur reaction with an environmentally safe and cost-competitive method using a thermal sulfur cracker cell. The elevated cracking-zone temperature enhanced the reactivity of sulfur by cracking evaporated sulfur molecules into smaller molecules, and resulted in the formation of a high-quality ZnS phase maintaining a low substrate temperature. The fabricated ultra-thin ZnS film played an excellent role as a buffer layer of the Cu(In,Ga)Se₂ thin-film solar cell, as the film showed high photovoltaic performances.