Polymer passivation has been leveraged to improve photodetection in two-dimensional transition metal dichalcogenide field-effect transistors. The relative passivation effects of common polymers, however, are not well understood. In this work, the interface of monolayer MoS2 and three common polymers, parylene N (Pa-N), polymethyl methacrylate (PMMA), and polyvinylidene difluoride trifluoroethylene (PVDF-TrFE), is assessed with multiple spectroscopic methods. Raman and photoluminescence spectroscopy demonstrate that Pa-N and PMMA provide an n doping effect, which increases photoconductivity and photogenerated charge in terahertz domain and time-resolved spectroscopy. Terahertz time-resolved spectroscopy shows significantly longer carrier lifetime for MoS2 coated with PVDF-TrFE compared to other polymers. These results suggest that PVDF-TrFE provides a unique benefit for photodetection applications.