Single source precursor for vacuum evaporation of MoBi2Se5 photoactive thin films

Abstract

In this paper, we report a new approach for deposition of nanocrystalline MoBi 2 Se 5 thin films using vacuum evaporation employing single source precursor synthesized by arrested precipitation technique. As deposited and vacuum annealed MoBi 2 Se 5 thin films were characterized for opto-structural, morphological, compositional and electrochemical analysis. It was observed that optical band gap decreases from 2.07 eV to 1.87 eV with vacuum annealing. X-ray diffraction studies confirm rhombohedral crystal structure of MoBi 2 Se 5 thin films. Scanning electron microscopy images show compact arrangement of spherical grains without pin holes. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) results reveal nanocrystalline nature having particle size *100 nm and selected area electron diffraction (SAED) pattern confirms rhombohedral crystal structure. The compositional analysis done by XPS shows presence of Mo 4? , Bi 3? and Se 2-oxidation states confirming stoichiometric MoBi 2 Se 5 thin film material. The photoelectrochemical (PEC) parameters of as deposited and vacuum annealed thin films were recorded in 0.5 M aqueous polysulfide electrolyte. Our PEC results show that 0.57 and 0.70 % conversion efficiency for as-deposited and vacuum annealed samples respectively.