Optoelectronics based on Vertical Transport in Multi-layer MoS2

High photon absorption and photoconductive gain observed in 2D Transition Metal Dichalcogenides make them exciting candidates for high performance photodetectors and photovoltaics [1]. However, slow response times and low $\mathrm{V}_{\mathrm{oc}}$ (open circuit voltage) have hindered the development of reliable optoelectronic devices [1]. Most attempts to mitigate these disadvantages involve fabrication of complex heterostructures [2]–[4], which may render them unfit for large area production. Besides, almost all reports on MeSi-bascd opto-electronics exploit its lateral transport while studies on vertical transport towards detectors and photovoltaics are at an embryonic stage. In this work, we demonstrate that a facile vertical metal/multilaycr-Mo'Sc/rnctal device can be engineered to enable both excellent photodetectors (with high responsivity $> 3\mathrm{A}/\mathrm{W}$ & good speed ~ 1 ms) OR high $\mathrm{V}_{\mathrm{oc}}(\sim 0.5\mathrm{V})$ photovoltaics. We adopt a conscious design strategy of employing vertical instead of lateral transport through multilayer Mos2 as this provides both larger area for photon absorption, as well as short charge transfer length (enabling effective separation) [Fig l(a)].