Polymer-based gate dielectrics have received growing attention due to their important role in field-effect transistors (OFETs). This review article aims to present the recent progress of polymer dielectrics for high-performance OFET applications. We first discuss the requirements for polymer dielectrics in tailoring the overall performance of OFETs from the perspective of both bulk material properties and surface characteristics of the polymers. On this basis, we introduce the design strategies and desired processing techniques of polymer dielectrics for optimizing the charge transport and stabilizing the operation of OFETs. Then, we highlight the recent advances in polymer-based dielectrics by classifying and comparing different categories of polymeric materials as well as polymer nanocomposites, and focus is also given to elucidating the critical relationships between polymer structures, gate dielectric properties and OFET performance. Finally, a perspective of future research directions and challenges for polymer dielectrics is provided.

Extrinsic hysteresis effects are often observed in MoS2 field effect devices due to adsorption of gas molecules on the surface of MoS2 channel. Scaling is a common method used in ferroics to quantitatively study the hysteresis. Here, the scaling behavior of hysteresis in multilayer MoS2 field effect transistors with a back-gated configuration was investigated. The power-law scaling relations were obtained for hysteresis area (⟨A⟩) and memory window (ΔV) with varying the region of back-gate voltage (Vbg,max). It is interesting to find that the transition voltage in the forward sweep (VFW) and in the backward sweep (VBW) shifted to the opposite directions of back-gate voltage (Vbg) with increasing Vbg,max. However, when decreasing Vbg,max, VFW shifted to positive and reversibly recovered, but VBW almost kept unchanged. The evolution of ⟨A⟩, ΔV, VFW, and VBW with Vbg,max were discussed by the electrons transferring process between the adsorbate and MoS2 channel.

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Wide-angle imaging is an important function in photography and projection, but it also places high demands on the design of the imaging components of a camera. To eliminate the coma caused by the focusing of large-angle incident light, traditional wide-angle camera lenses are composed of complex optical components. Here, we propose a planar camera for wide-angle imaging with a silicon nitride metalens array mounted on a CMOS image sensor. By carefully designing proper phase profiles for metalenses with intentionally introduced shifted phase terms, the whole lens array is capable of capturing a scene with a large viewing angle and negligible distortion or aberrations. After a stitching process, we obtained a large viewing angle image with a range of > 120 ∘ using a compact planar camera. Our device demonstrates the advantages of metalenses in flexible phase design and compact integration, and the prospects for future imaging technology.