Optoelectronic Properties of Two-Dimensional Monochalcogenides

Two-dimensional group-IV monochalcogenides, typified by monolayer SnS, SnSe, GeS and GeSe, exhibit exceptional optoelectronic characteristics arising from their reduced dimensionality and intrinsic structural anisotropy. Confinement of charge carriers in the atomically thin plane enhances exciton binding energies and nonlinear optical responses, while their orthorhombic crystal symmetry produces distinct armchair and zigzag directions with markedly different absorption, emission and carrier-mobility profiles. Tunable direct band-gaps spanning the visible to near-infrared, coupled with low thermal conductivity and high electrical conductivity, render these materials attractive for photodetectors, photovoltaics and on-chip photonic devices. Van der Waals stacking of disparate monochalcogenide layers or integration with other two-dimensional crystals enables further band-structure engineering through interlayer coupling or twist-induced moiré potentials. Rapid progress in scalable exfoliation and solution processing, allied to emerging device architectures, underscores the global significance of these materials for flexible, self-powered and multispectral optoelectronic systems.

Research from Nature Portfolio

Recent studies have demonstrated optical access and control of the valley degree of freedom in Tin(II) sulfide at ambient conditions, identifying two non-degenerate valleys with distinct direct band-gap energies and achieving polarisation-selective absorption and emission efficiencies approaching 96%. This work establishes a platform for room-temperature valleytronics in monochalcogenides. Complementary first-principles investigations of few-layer IV–VI materials have revealed pronounced red- and blue-shifts of characteristic Raman modes as a function of thickness, providing a nondestructive probe of layer number and insights into weak interlayer bonding. In parallel, the bottom-up synthesis of twisted heterostructures via aligned van der Waals epitaxy and solid-state transformation has opened a route to scalable fabrication of angle-defined stacks, enabling moiré superlattice potentials for band-structure tuning and novel optoelectronic phenomena.

Optoelectronic Properties of Two-Dimensional Monochalcogenides publication trend

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

Technical terms

Exciton: A bound state of an electron and a hole attracted by Coulomb interaction, crucial for optical absorption in two-dimensional semiconductors.

Van der Waals heterostructure: A stack of atomically thin layers held together by weak interlayer forces, enabling customised band alignments.

Anisotropy: Directional dependence of electronic or optical properties resulting from crystal symmetry.

Valley degree of freedom: Distinct local energy extrema in the electronic band structure that can be selectively addressed by polarised light.

Quantum confinement: Modification of electronic states and optical transitions due to spatial restriction of carriers in low-dimensional systems.

References

1. Self‐powered transparent photodetector for subretinal visual functions of wide‐field‐of‐view and broadband perception. InfoMat (2023).
2. Van Der Waals Semiconductor Based Omnidirectional Bifacial Transparent Photovoltaic for Visual‐Speech Photocommunication. Advanced Science (2023).
3. Thermoelectric and phonon transport properties of two-dimensional IV–VI compounds. Scientific Reports (2017).
4. Tin(II) Sulfide (SnS) Nanosheets by Liquid-Phase Exfoliation of Herzenbergite: IV–VI Main Group Two-Dimensional Atomic Crystals. Journal of the American Chemical Society (2015).
5. Accessing valley degree of freedom in bulk Tin(II) sulfide at room temperature. Nature Communications (2018).
6. Raman Spectra Shift of Few-Layer IV-VI 2D Materials. Scientific Reports (2019).
7. Self-organized twist-heterostructures via aligned van der Waals epitaxy and solid-state transformations. Nature Communications (2019).
8. Quantum confinement-induced enhanced nonlinearity and carrier lifetime modulation in two-dimensional tin sulfide. Nanophotonics (2020).