Surfactant assisted synthesis of nanocrystalline n-Bi$_2$Se$_3$ thin films at room temperature via arrested precipitation technique

In the present investigation, we have successfully synthesized nanocrystalline bismuth selenide (Bi$_2$Se$_3$) thin films using an arrested precipitation technique at room temperature. The optostructural, morphological, compositional and photoeletrochemical properties were studied for Bi$_2$Se$_3$ thin films prepared via surfactant-assisted synthesis. The optical study reveals the presence of direct allowed transition with band gap energy ranging from 1.40-1.80 eV. The X-ray diffraction (XRD) pattern confirms rhombohedral crystal structure. Scanning electron microscopy study shows the morphological transition from an interconnected mesh to nanosphere-like morphology and finally, lamellar sphere. Atomic force microscopy (AFM) study carried out to determine surface roughness and surface topography of thin films. Energy dispersive spectroscopy (EDS) analysis reveals the presence and ratio of elemental bismuth and selenium. Finally, the photoelectrochemical (PEC) performance of all the as-synthesized thin films were carried out using iodidepolyiodide redox couple.