Photodetectors based on two-dimensional (2D) materials have been the focus of intensive research and development over the past decade. However, a gap has long persisted between fundamental research and mature applications. One of the main reasons behind this gap has been the lack of a practical and unified approach for the characterization of their figures of merit, which should be compatible with the traditional performance evaluation system of photodetectors. This is essential to determine the degree of compatibility of laboratory prototypes with industrial technologies. Here we propose general guidelines for the characterization of the figures of merit of 2D photodetectors and analyze common situations when the specific detectivity, responsivity, dark current, and speed can be misestimated. Our guidelines should help improve the standardization and industrial compatibility of 2D photodetectors.

With the continuous advancement of nano‐fabrication techniques, development of novel materials, and discovery of useful manipulation mechanisms in high‐performance applications, especially photodetectors, the morphology of junction devices and the way junction devices are used have been fundamentally revolutionised. Simultaneously, new types of photodetectors that do not rely on any junction, providing high signal‐to‐noise ratio and multidimensional modulation, have also emerged. This review outlines a unique category of material systems supporting novel junction devices for high‐performance detection, namely the van der Waals materials, and systematically discusses new trends in the development of various types of devices beyond junctions. This field is far from mature and there are numerous methods to correctly measure and evaluate photodetectors. Therefore, we also aim to provide a solution from the perspective of applications in this review. Finally, based on the insight into the unique properties of the material systems and the underlying microscopic mechanisms, emerging trends in junction devices are discussed, a new morphology of photodetectors is proposed, and some potential innovative directions in the subject area are suggested.This article is protected by copyright. All rights reserved

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