Binary chalcogen alloys: structural evolution and versatile applications

Binary chalcogen alloys, including sulfur-selenium (S-Se), sulfur-tellurium (S-Te) and selenium-tellurium (Se-Te), exhibit composition-dependent structural diversity and tunable functional properties arising from the interplay of atomic-size mismatch and distinct bonding characteristics. By combining the intrinsic merits of S, Se, and Te, these alloys offer tunable bandgaps, enhanced electrical conductivity, and adaptable mechanical and dielectric properties, enabling applications in energy storage, dielectric devices, photovoltaics, and photodetection. Herein, we systematically review recent advances in these three binary chalcogen alloy systems, with particular emphasis on their composition-dependent structural evolution, including the coexistence and transformation of ring and chain motifs, as well as the formation of heterogeneous local structures. We further summarise their emerging and established applications in batteries, dielectric and memristive devices, solar cells, broadband photodetectors, and neuromorphic electronics. Finally, we highlight key challenges and future opportunities for the development of binary chalcogen alloys.