A facile synthetic route to tungsten diselenide using a new precursor containing a long alkyl chain cation for multifunctional electronic and optoelectronic applications

Abstract

Single source precursors for coating and subsequent thermal decomposition processes enable a large-scale, low-cost synthesis of two-dimensional transition metal dichalcogenides (TMDs). However, practical applications based on two-dimensional TMDs have been limited by the lack of applicable single source precursors for the synthesis of p-type TMDs including layered tungsten diselenide (WSe₂). We firstly demonstrate the simple and facile synthesis of WSe₂ layers using a newly developed precursor that allows improved dispersibility and lower decomposition temperature. We study the thermal decomposition mechanism of three types of (Cat⁺)₂[WSe₄] precursors to assess the most suitable precursor for the synthesis of WSe₂ layers. The resulting chemical and structural exploration of solution-processed WSe₂ layers suggests that the (CTA)₂[WSe₄] may be a promising precursor because it resulted in the formation of high-crystalline WSe₂. In addition, this study verifies the capability of WSe₂ layers for multifunctional applications in optoelectronic and electronic devices. The photocurrent of WSe₂-based photodetectors shows an abrupt switching behavior under periodic illumination of visible or IR light. The extracted photoresponsivity values for WSe₂-based photodetectors recorded at 0.5 V correspond to 26.3 mA W⁻¹ for visible light and 5.4 mA W⁻¹ for IR light. The WSe₂-based field effect transistors exhibit unipolar p-channel transistor behavior with a carrier mobility of 0.45 cm² V⁻¹ s⁻¹ and an on-off ratio of ∼10.