Spectrometers are the devices which can acquire multi-dimensional information of incident light including intensity and wavelength. They have broad applications in both laboratory and industrial fields. Nevertheless, spectrometers relying on gratings or Michelson interferometers are inherently bulky, which restricts their integration and deployment in portable devices. Consequently, the miniaturization and on-chip integration of spectrometers are crucial for the advancement of next-generation optoelectronic devices. Two-dimensional (2D) materials, with unique characteristics including atomic-scale thickness, absence of surface dangling bonds, and versatile band structure modulation capabilities, show great potential for fabricating on-chip miniature spectrometers.

This review focuses on micro-spectrometers with minimal electrodes based on 2D materials, and provides a detailed analysis of their device configurations, working principles, advantages, and existing limitation. Unlike array-based or tunable-filter spectrometers, the devices with few-electrode architectures utilize physical effects such as the Stark effect, quantum tunneling, and electrostriction to encode spectral information into electrical signals, thereby achieving spectral reconstruction and greatly reducing device footprint and complexity. We conduct a systematic categorization and evaluation of representative implementations of these spectrometers. Through a comparison of their key metrics, such as spectral resolution, operational bandwidth, response speed, and reconstruction accuracy, we clarify the underlying physical mechanisms that determine their performance. In addition to conducting a comprehensive survey of cutting-edge devices, we perform a critical assessment of the long-standing challenges within the field. These challenges include the scalable and reproducible material synthesis, the stable integration of devices with silicon photonics and readout circuits, the environmental stability of 2D materials, and the optimization of computational algorithms for reliable spectral retrieval under the conditions of noise or limited data. Finally, we outline future research directions with the aim of improving device performance and putting them into practical applications in on-chip photonic systems. This review is expected to provide useful information for researchers engaged in the research on ultra compact miniaturized spectrometers and to promote innovation in ultra compact spectral sensing technologies.