Highly Tunable, Broadband, and Negative Photoresponse MoS₂ Photodetector Driven by Ion-Gel Gate Dielectrics

Abstract

Revealing the light–matter interaction of molybdenum disulfide (MoS2) and further improving its tunability facilitate the construction of highly integrated optoelectronics in communication and wearable healthcare, but it still remains a significant challenge. Herein, polyvinylidene fluoride and 1-ethyl-3-methylimidazolium bis­(trifluoromethylsulfonyl)­imide (PVDF-EMIM-TFSI) ion-gel are employed to replace the oxide to fabricate a MoS2-based phototransistor. The high capacitance enables a large tunability of the carrier concentration that results in ambipolar transport of MoS2. It is found that the photoelectrical effect of the MoS2 ion-gel phototransistor can be greatly tuned by the gate voltage including its photoresponsivity, detectivity, and response wavelength. An abnormal negative photoelectrical effect in both the electron branch and the hole branch is observed which is due to the adsorption/desorption of the C2F6NO4S2 – ion. By tuning the carrier concentration, the photoresponse can be extended from the visible region to the short infrared region. At 1200 nm, the photoresponse and detectivity can be tuned as large as 0.90 A/W and 1.88 × 1011 Jones, respectively. Ultimately, by combining the tunability of gate voltage and wavelength, it is demonstrated that the photoelectrical effect is dominated by the photogating effect in the hole carrier, while it is coregulated by a photogating and photothermal effect in electron carrier. This study provides new insights for developing a highly tunable broadband photodetector with low consumption.

Emerging MoS2 Wafer-Scale Technique for Integrated Circuits

“…In recent years, two-dimensional atomic crystals have shown rich physical properties due to their atomic thickness, high carrier mobility, and easily adjustable electronic structure, which makes them essential research value not only in the discussion of physical mechanisms but also in the design and potential application of devices. In the field of photoelectric detection, on the one hand, the channel volume of optoelectronic devices based on two-dimensional atomic crystals will be significantly reduced (the thickness of the absorption layer is about 1 ~ 5 nm), and the intrinsic dark current proportional to the device volume will be significantly reduced [155][156][157]. At the same time, after the longitudinal transport is limited, the carrier is easily regulated by the local field in the transverse transport, and photoelectric detection with a high signal-to-noise ratio is expected to be realized at room temperature.…”

Negative Photoconductivity: Bizarre Physics in Semiconductors

“…As we discussed in the above sections that NPC was widely observed in various types of materials. ,,,,− Different origin has been proposed for NPC generation, which can be suitable for various kind of applications. The NPC effect has been used for the fabrication of humidity and light sensors, highly sensitive photodetectors, and nonvolatile memories. ,− Qin et al demonstrated that the NPC in nanodiamonds can be applied for humidity sensors with the sensitivity of 1.26 × 10 6 %, which is the highest in carbon-based humidity sensors . Zhuang et al showed the application of NPC in humidity sensors with a responsivity of 418.1 μAW –1 (at high humid RH = 90%) .…”

Modulate the Interfacial Oxygen Vacancy for High Performance MoS2 Photosensing−Memory Device

“…To quantify how such response behavior relates to illumination, a new parameter is demanded. Normally, the responsivity is calculated through Equation : [ 48,49 ] $$\[ \begin{array}{*{20}{c}}{R = {I_{{\rm{ph}}}}{\rm{/PS}}}\end{array} \]$$where the photocurrent is a measurement of the response. However, in this work, to clearly reveal the tunable hysteresis behavior of the transistor, we redefine the responsivity, using the loop width's difference to measure the photoresponse in Equation : $$\[ \begin{array}{*{20}{c}}{{R^ * } = \left( {{U_p} - {U_d}} \right){\rm{/PS}}}\end{array} \]$$where U p and U d are the hysteresis width with and without illumination, P is the power density and S is the device area.…”

“…To quantify how such response behavior relates to illumination, a new parameter is demanded. Normally, the responsivity is calculated through Equation 1: [48,49] R I /PS ph =…”