Photogalvanic Effects in Two-Dimensional Materials

The photogalvanic effect encompasses a class of second‐order non-linear optoelectronic phenomena whereby illumination generates a direct electric current in the absence of junctions or external bias. In two-dimensional materials, broken inversion symmetry, strong spin–orbit coupling and reduced dimensionality conspire to yield both linear and circular photogalvanic responses. These effects arise from asymmetric excitation of charge carriers in momentum space, and can be tuned via crystal symmetry, interface engineering and external fields. Monolayer transition-metal dichalcogenides exhibit pronounced circular photogalvanic currents linked to valley-selective optical transitions, while Janus structures and engineered grain-boundary architectures unlock giant bulk photovoltaic effects beyond conventional limits. In magnetic and graphene-based systems, spin-polarisation antisymmetry and edge-state modulation enable pure spin currents under illumination. Such photogalvanic mechanisms offer routes to on-chip polarisation detectors, spintronic generators and highly efficient solar-energy converters, underscoring their global significance for optoelectronic and energy-harvesting technologies.

Research from Nature Portfolio

Recent studies have revealed a giant intrinsic bulk photovoltaic effect in van der Waals grain boundaries of layered semiconductors, achieving record photocurrent densities via broken inversion symmetry at one-dimensional interfaces. In monolayer molybdenum disulphide, strong excitonic resonances and spin–valley coupling give rise to dichroic photocurrent responses of up to sixty per cent, harnessing the circular photogalvanic effect for valley-selective current generation. Investigations of circular photocurrents in monolayer molybdenum diselenide have further clarified the symmetry and bias dependencies of competing contributions, demonstrating that reduced device symmetry is essential for helicity-driven charge and spin flows, and that Berry curvature plays a subordinate role in the observed effects.

Photogalvanic Effects in Two-Dimensional Materials publication trend

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

Technical terms

Photogalvanic effect: Generation of a direct current under uniform illumination due to spatial and symmetry-induced asymmetry in carrier excitation.
Bulk photovoltaic effect (BPVE): Intrinsic second-order photocurrent in non-centrosymmetric materials that exceeds the Shockley-Queisser limit by enabling carrier generation without p-n junctions.
Circular photogalvanic effect (CPGE): Photocurrent induced by circularly polarised light, sensitive to material chirality and valley or spin degrees of freedom.
Berry curvature: Geometric property of electronic bands influencing anomalous velocities and contributing to non-linear optical responses.
Valleytronics: Exploitation of momentum-space valleys in two-dimensional semiconductors as a degree of freedom for information processing.
Rashba spin–orbit interaction: Spin splitting of electronic bands due to structural inversion asymmetry, crucial for spin-dependent photogalvanic responses.

References

1. Giant intrinsic photovoltaic effect in one-dimensional van der Waals grain boundaries. Nature Communications (2024).
2. Dichroic spin–valley photocurrent in monolayer molybdenum disulphide. Nature Communications (2015).
3. Symmetry regimes for circular photocurrents in monolayer MoSe2. Nature Communications (2018).
4. Photogalvanic Effect in Nitrogen-Doped Monolayer MoS2 from First Principles. Discover Nano (2019).
5. Two-dimensional centrosymmetrical antiferromagnets for spin photogalvanic devices. npj Quantum Information (2021).
6. Light-induced pure spin current in carbon hexagonal-connected zigzag graphene nanoribbons via magnetic field modulation.. Optics Express (2023).