Tuneable photoconductivity and mobility enhancement in printed MoS 2 /graphene composites

Abstract

With the aim of increasing carrier mobility in nanosheet-network devices, we have investigated MoS2–graphene composites as active regions in printed photodetectors. Combining liquid exfoliation and inkjet-printing, we fabricated all-printed photodetectors with graphene electrodes and MoS2–graphene composite channels with various graphene mass fractions (0 ≤ M f ≤ 16 wt%). The increase in channel dark conductivity with M f was consistent with percolation theory for composites below the percolation threshold. While the photoconductivity increased with graphene content, it did so more slowly than the dark conductivity, such that the fractional photoconductivity decayed rapidly with increasing M f. We propose that both mobility and dark carrier density increase with graphene content according to percolation-like scaling laws, while photo-induced carrier density is essentially independent of graphene loading. This leads to percolation-like scaling laws for both photoconductivity and fractional photoconductivity—in excellent agreement with the data. These results imply that channel mobility and carrier density increase up to 100-fold with the addition of 16 wt% graphene.