Multi-layered MoS₂ phototransistors as high performance photovoltaic cells and self-powered photodetectors

Abstract

Optoelectronic diode based on p-n junction is one of the most fundamental device building blocks with extensive applications. Compared with graphene, layered transition-metal dichalcogenides demonstrate promising applications in novel valley-electronics and opto-electronics. Here we reported the fabrication and optoelectronic properties of a single multilayer MoS 2 sheet. Our results indicate that the thin MoS 2 shows linear transport property while thick MoS 2 shows diode characteristic with well-defined current rectification behavior. We assign that the rectification behavior is due to the formation of p-n junction in the single multilayer MoS 2 piece. The intrinsic defects in MoS 2 can change the conduction polarity. Such as: sulfur vacancies contribute to the n-type behavior while sulfur interstitials and molybdenum vacancies contribute to the p-type conduction. The variation of intrinsic defect and stoichiometry is obvious over the micrometer range in thick MoS 2 . The fabricated MoS 2 transistors were assessed under bias and gate voltage modulation with exposed to red, green and UV light at vacuum. The multilayer MoS 2 shows dominant p-type behavior under dark condition while shows dominant n-type conduction under light illumination. In addition, this MoS 2 phototransistor shows evident photovoltaic effect. The open-circuit voltage (V oc ) and short-circuit current (I sc ) are observed to be -0.48 V and 494 nA under red illumination. These results demonstrate the potential application of single multilayer MoS 2 sheet in optoelectronics, such as light-emitting diodes (LEDs), field-effect photovoltaic cells and photodetectors.

Large-Area Ultraviolet Photodetectors Based on p-Type Multilayer MoS2 Enabled by Plasma Doping

“…The time-resolved characteristics revealed a reliable photoresponse with a stabilized photocurrent, as shown in Figure 5d. Under 365 nm illumination, the photocurrent of the MoS 2 PFET increased rapidly after exposure to UV radiation, with a rise time of 37 ms, significantly faster than those of other reported MoS 2 photodetectors [3,4,15,26], as shown in Figure 5e. This photocurrent remained nearly constant during the UV exposure (10 s) and decayed quickly during dark conditions with a decay time of approximately 39 ms.…”

Van der Waals MoS2/VO2 heterostructure junction with tunable rectifier behavior and efficient photoresponse

“…At room temperature, a maximum photoresponsivity of 1.25 A/W was measured at 550 nm, and values exceeding silicon photodiode performance have been obtained in the 500/650 nm range 13 . Responsivity values larger than one have already been reported in p-n junctions based on doped multilayer MoS 2 flakes, and can be attributed to the efficient photocarrier separation operated by the built in voltage of the junction 21 , 22 . The photoresponsivity in the visible range is clearly boosted by the temperature rise and tends to saturate above the VO 2 IMT temperature.…”

Large‐area growth of multi‐layered MoS2 for violet (∼405 nm) photodetector applications

“…To understand the behaviour of I – V curve of the multi‐layered MoS 2 ‐based violet PDs, it is necessary to consider the work functions of MoS 2 and Au contacts. In general, the work function of n‐type MoS 2 , Ti, and Au has been reported to be about ∼4.7, 4.3, and 5.1 eV, respectively, while the electron affinity of n ‐type MoS 2 to be 4.4–4.6 eV . The ohmic contact with low barrier height (0.1–0.3 eV) could be expected between MoS 2 and Ti due to their small potential difference.…”

“…). For the MoS 2 , it naturally indicates n‐type conductivity and there are some trap levels within its band gap due to the disorders and sulfur vacancies . Under the dark state, these free electrons are combined with the O 2 and water molecules in air.…”