Stable, highly-responsive and broadband photodetection based on large-area multilayered WS2 films grown by pulsed-laser deposition†
The progress in the field of graphene has aroused a renaissance of keen research interest in layered transition metal dichalcogenides (TMDs). Tungsten disulfide (WS2), a typical TMD with favorable semiconducting band gap and strong light–matter interaction, exhibits great potential for highly-responsive photodetection. However, WS2-based photodetection is currently unsatisfactory due to the low optical absorption (2%–10%) and poor carrier mobility (0.01–0.91 cm2 V−1 s−1) of the thin WS2 layers grown by chemical vapor deposition (CVD). Here, we introduce pulsed-laser deposition (PLD) to prepare multilayered WS2 films. Large-area WS2 films of the magnitude of cm2 are achieved. Comparative measurements of a WS2-based photoresistor demonstrate its stable broadband photoresponse from 370 to 1064 nm, the broadest range demonstrated in WS2 photodetectors. Benefiting from the large optical absorbance (40%–85%) and high carrier mobility (31 cm2 V−1 s−1), the responsivity of the device approaches a high value of 0.51 A W−1 in an ambient environment. Such a performance far surpasses the CVD-grown WS2-based photodetectors (μA W−1). In a vacuum environment, the responsivity is further enhanced to 0.70 A W−1 along with an external quantum efficiency of 137% and a photodetectivity of 2.7 × 109 cm Hz1/2 W−1. These findings stress that the PLD-grown WS2 film may constitute a new paradigm for the next-generation stable, broadband and highly-responsive photodetectors.