Multifunctional Nanocrystalline W(Se 0 . 5 S 0 . 5 ) 2 Thin Films: A Promising Material for Thermoelectric and Photoelectrochemical Devices

ABSTRACT Transition metal dichalcogenides alloys are promising materials for tunable optoelectronic and energy applications; however, systematic studies on chemically deposited ternary tungsten chalcogenide thin films remain limited. In this work, W(Se 0 . 5 S 0 . 5 ) 2 thin films were synthesized on glass substrates using chemical bath deposition with citric acid as a complexing agent. The objective of this study is to explore the influence of sulfur–selenium alloying on the structural, optical, electrical, thermoelectric, and photoelectrochemical properties of the films. X‐ray diffraction confirms the formation of a single‐phase hexagonal 2H structure with lattice parameters a = 3.26 Å and c = 12.84 Å. Scanning electron microscopy reveals compact, platelet‐like nanocrystalline morphology, while energy‐dispersive x‐ray analysis confirms stoichiometric composition. Optical measurements show strong visible–NIR absorption with a direct band gap of 1.72 eV, indicating effective band gap tuning. Electrical studies exhibit thermally activated semiconducting behavior with activation energy of 0.18 eV. The films show p‐type conductivity with Seebeck coefficients of 200.5 µV K − 1 at 300 K and 262 µV K − 1 at 525 K. Photoelectrochemical measurements demonstrate a conversion efficiency of 1.17%. These results highlight the potential of W(Se 0 . 5 S 0 . 5 ) 2 thin films for multifunctional optoelectronic, thermoelectric, and energy conversion applications.