Photoresponse of Stacked, Multilayer MoS2 Films Assembled from Solution-Processed MoS2 Flakes

Taking a solution-based approach to obtain transition metal dichalcogenide monolayers affords a number of advantages, including processing that is scalable, cost effective, and enables tuning monolayer functionality through solution chemistry. MoS 2 flakes down to monolayers prepared using such an approach have demonstrated improved photoluminescence and tuned solubility. Developing methods for assembling such MoS 2 flakes from solution to fashion integrated, heterostructure devices provides opportunities for exploring and potentially applying these materials. In this study, we describe a simple method for stacking two-dimensional network films (2DFs) layer-by-layer on different substrates by first depositing a 2DF on an alumina membrane, transferring the 2DF to a gel film, and dry transferring to the desired substrate. The method allows control over chemical nature, shape, and position of each layer in the stacked, multilayer 2DF. The present study shows that stacked multilayers exhibit increased electrical conductivity with increasing number of layers and photoconductivity upon illumination using a white LED. Combined with ionic liquid gating, 2DFs exhibit a photoresponsivity of 36 mA/W, more than two orders higher than previously reported using a device based on MoS 2 prepared in solution. Given its scalability and facility for device fabrication, this approach opens a diversity of applications for solution-based 2D materials.