Robust Photodetectable Paper from Chemically Exfoliated MoS₂-MoO₃ Multilayers

Photodetectors, which are capable of detecting light with varied wavelength, have nowadays been widely applied onto emerging fields such as security, entertainment, healthcare, environment, and so on. As the one with a two-dimensional layered structure, molybdenum disulfide (MoS₂) possesses striking optical and electrical properties that can be used in photodetecting, yet the challenges remain in terms of material processing, device fabrication simplicity, and enhancement of overall photodetection performance. In this work, a photodetectable paper based on a mixture of double-phased MoS₂ (1T and 2H) and MoO₃ was successfully fabricated through a straightforward route, that is, chemical exfoliation and deposition of MoS₂ powder on a flexible cellulose ester membrane, followed by inkjet-printed PEDOT:PSS as electrodes. The obtained device shows varied sensitivity to the light with different wavelengths. Compared with that under green and red lights, the prepared photodetector has the highest internal quantum efficiency (0.063%) and responsivity (0.134 mA W^-1), while having longest response/recovery time (17.5/15.3 s) when illuminated with purple light (405 nm). The achieved responsivity is much higher than other reported liquid exfoliation- and solution-derived MoS₂ photodetectors. This is ascribed to (1) the enhanced photoelectron generation caused by both MoS₂ and MoO₃ and (2) the good electric conductivity and efficient charge transport caused by the metallic 1T MoS₂. This work demonstrates the feasibility of fabricating the MoS₂-based photodetector with excellent performance through a simple exfoliation/filtration and inject printing route, and the detailed study on the response to light with different wavelengths unveils the interaction between the device and the incident light, further broadening the potential applications of such design.