Growth, Structural Characteristics and Photoelectrochemical Behaviour of Tungsten Diselenide (WSe2) Single Crystals

Studies in regard to structural and photoelectrochemical (PEC) properties of tungsten diselenide (n‐WSe2) single crystals grown by vapour transport technique have been carried out. X‐ray diffraction (oscillation) study reveals α curious two layer lines attributable to more than one a lattice parameters coexistence of nonstoichiometric phases is thought to lead to dual α lattice parameters (3.08 Å and 2.80 Å) observed. Surface studies with optical and scanning electron microscopic techniques revealed that the crystal surfaces possess varying density of surface steps. The photoelectrochemical behaviour of n‐WSe2 electrodes examined with stepped and stepfree surfaces reveals that the steps have significant influence on the PEC behaviour. Crystals with stepfree surfaces exhibited better photoresponse as evidenced by improved photopotential (520 mV) and photocurrent density (7.5 mA/cm2). Moreover, the improved photoresponse of n‐WSe2 crystal electrodes in the present study, as compared to the previous investigation, is expected to arise from the existence of different structural phases in the as‐grown crystals (dual phases) which can lead to tandemization effect with consequent improvement in photoresponse.