Low-Cost, Homogeneous, and Continuous Thin Film of 2D Semiconductors: Towards Large Scale Electronic and Photonic Devices

2-Dimensional (2D) materials are emerging new materials with promising future. Yet, as the demand for 2D large-scale applications increases, major nanofabrication challenges arise which could hinder the implementation of 2D materials for device applications. Liquid-phase exfoliation is a promising route to integrate nanomaterials into large-scale applications. This method has been recently reported by some groups as an inexpensive and facile method to yield high quality few-layer materials. In particular, thin films produced from drop casting/Ink-jet printing of 2D-materials on silicon substrate typically yields non-uniform distribution of nanoparticles, which is significantly attributed to the “Coffee Ring Effect”, which led to introducing additives and surfactants to 2D ink solutions and potentially altering the pristine nature of the fabricated thin film. In this work, we apply liquid phase exfoliation technique on WSe2 powder through suspension in 1:1 Water/Ethanol mixture. We show an induced suppression of the Coffee-ring transport mechanism by controlling evaporation of the solution droplet, which has led to homogenous and continuous thin films. We apply our method to create WSe2/n-type Si photovoltaic devices and characterize the photovoltaic properties under 532nm laser irradiation. Our results shed some light on low-cost fabrication processes of 2D thin films for large-scale electronic and photonic applications.