Polymorphism in the oxysulfide system LaOInS 2 and its selenide derivatives: impact on the bandgap and photocurrent response

■ Selenium substitution stabilize the layered phase ■ Limit of insertion of selenium is below 75% in α Two synthesis pathways: two different polymorphs: ■ Thermodynamically stable α-phase via direct solid-state reaction in sealed quartz tube at 800°C of In 2 S 3 La 2 S 3 and La 2 O 3 ■ The layered via metathesis from LaOCl and NaInS 2 ■ LaOCl and NaInS 2 heated at 850°C yield Layered phase and transform to α at higher temperatures (ref. 2) Polymorphism of LaOInS 2