Synthesis, characterization, and photoelectrochemical performance of nanocrystalline ternary Mo_xBi_(2−x)Se₃ mixed metal chalcogenide thin films

Abstract

In the present investigation, a series of molybdenum-doped bismuth selenide (Mo_xBi_(2−x)Se₃) (x = 0.01 to 0.05) thin films have been deposited by simple and low-cost arrested precipitation technique (APT) onto substrate for the first time. The deposition has been carried out from aqueous alkaline bath using nonhazardous triethanolamine as a complexing agent at low temperature. The deposited thin films have been characterized to study optical, structural, morphological, compositional, electrical, and photoelectrochemical properties by using UV–Vis, XRD, SEM, AFM, TEM, SAED, EDS, XPS, EC, TEP, and PEC techniques. In the series of Mo_xBi_(2−x)Se₃ thin films, properties were altered with increase in molybdenum content. Optical absorption study shows red shift of absorbance in visible region and reflected in bandgap energy, which decreases from 1.48 to 1.30 eV. The SEM images show granular surface morphology without any cracks and increases in particle size with Mo content in film. The AFM analysis shown average roughness of the film which is 4.79 nm/µm². TEM analysis gives agglomerated and granular morphology of the material. The SAED pattern gives excellent agreement with XRD results. EDS and XPS analysis confirms the presence of Mo, Bi, and Se elements with + 4, + 3, and − 2 oxidation states, respectively. From electrical conductivity measurements, activation energy was calculated and it decreases from 0.9565 to 0.1162 eV with increase in Mo content. Electrical conductivity increases with temperature indicates semiconducting nature of the films. TEP measurement shows negative Seebeck coefficient which confirms n-type semiconductor property. The PEC power conversion efficiency increases from 0.042 to 0.456% with increase in Mo content.