Graphene-Coated Substrate-Mediated Photoresponse from MoS2/ UCNP Nanohybrid-Based Photodetectors

Hybrids of two-dimensional (2D) and 0D nanoma-terials offer a wider spectrum of properties than their counterparts. Here, we choose a molybdenum disulfide and NaGdF4:Yb3+, Er3+ upconversion nanoparticle (MoS2-UCNP) nanocomposite (NC) on graphene (G)-coated polydimethylsiloxane (PDMS) and silica/ silicon (SiO2/Si) substrates as broadband photodetectors (PDs). The band gap (similar to 680 nm) limited response of pure MoS2 is broadened by the infrared (980 nm) absorbing UCNPs. Identically fabricated PDs on PDMS and SiO2/Si showed the highest photoresponsivity of 26.18 and 84.52 AW-1, respectively, under 661 nm laser illumination at a density of 1 mW/cm2 at 1 V bias. The MoS2-UCNPs/Graphene/SiO2/Si PD (SiO2/Si PD) showed a response time of similar to 100 ms compared to similar to 3 s for the PDMS-based PD. The PDMS-based PD showed a reasonably stable photocurrent, decaying by similar to 39%, under 250 repetitive cycles of 6.25% bending strain; a maximum decrease of similar to 40% of the photocurrent was observed under the 11.11% bending strain compared to the as-prepared flat PD. Both devices could detect signals from domestic appliances such as air conditioner remotes, laser pointers, and cellphone flashlights. The flexible PD based on a hybrid of two nanomaterials having complementary ranges of absorption offers the possibility for better wearable sensors.