Optoelectronic Properties of Two-Dimensional Indium Selenide

Two-dimensional indium selenide (InSe) has emerged as a versatile semiconductor platform owing to its layer-dependent electronic structure, high carrier mobility and strong light–matter interactions. In its few-layer form, InSe exhibits a tunable band gap that spans the near-infrared to visible spectrum, transitioning from a direct to an indirect gap as thickness decreases. The van der Waals nature of InSe enables integration into heterostructures without lattice matching, while its intrinsic out-of-plane exciton orientation offers unique opportunities in hybrid photonic circuits. Exceptional photoresponsivity, rapid response times and anisotropic transport in certain polytypes further underpin its promise for next-generation photodetectors, optical modulators and flexible optoelectronic devices. Advances in controlling trap states, surface chemistry and junction engineering have paved the way for devices that can operate self-powered, emulate bionic visual adaptation or resolve polarisation without external filters. Collectively, these properties position two-dimensional InSe at the forefront of research into compact, energy-efficient optoelectronic systems with applications spanning imaging, sensing and on-chip photonics.

Research from Nature Portfolio

Recent studies have exploited the flat-band dispersion in gated few-layer InSe to electrically detect van Hove singularities at the valence-band edge. By correlating tunnelling photocurrents with ambipolar transport and photoluminescence, researchers have demonstrated a sharp transition in tunnelling mechanisms linked to the flat-band position, offering a robust probe up to room temperature. Complementary work has unveiled that InSe flakes sustain luminescent excitons with an intrinsic out-of-plane dipole orientation, in stark contrast to other transition-metal dichalcogenides. This discovery, supported by far-field photoluminescence mapping and ab initio calculations, highlights InSe’s suitability for integrated photonic chips that exploit vertical emission. Foundational investigations using density functional theory and high-field magneto-optics have elucidated the layer-dependent direct-to-indirect band-gap crossover, demonstrating finely tuneable optical response from two-layer InSe to bulk and revealing quantum-dot-like emission features across a wide energy range.

Optoelectronic Properties of Two-Dimensional Indium Selenide publication trend

The graph below shows the total number of articles in optoelectronic properties of two-dimensional indium selenide across all publications each year (not limited to Nature Index journals).

Technical terms

van der Waals crystal: A layered material in which individual atomic sheets are held together by weak van der Waals forces, enabling facile exfoliation and stacking of heterostructures.

van Hove singularity: A peak in the electronic density of states occurring at critical points in the band structure, often associated with unique optical and transport phenomena.

Exciton: A bound state of an electron and a hole in a semiconductor, whose recombination gives rise to photoluminescence.

Photogating effect: Modulation of a device’s conductance due to trapped photogenerated charges, which effectively gate the channel and amplify the photocurrent.

Photoresponsivity: The ratio of photocurrent generated to incident light power, typically expressed in amperes per watt (A W⁻¹), indicating the sensitivity of a photodetector.

References

1. Electrical detection of the flat-band dispersion in van der Waals field-effect structures. Nature Nanotechnology (2023).
2. Out-of-plane orientation of luminescent excitons in two-dimensional indium selenide. Nature Communications (2019).
3. The direct-to-indirect band gap crossover in two-dimensional van der Waals Indium Selenide crystals. Scientific Reports (2016).
4. Self-powered and broadband opto-sensor with bionic visual adaptation function based on multilayer γ-InSe flakes. Light: Science & Applications (2023).
5. The role of traps in the photocurrent generation mechanism in thin InSe photodetectors. Materials Horizons (2020).
6. High-performance polarization-sensitive photodetectors on two-dimensional β-InSe. National Science Review (2021).