2D Materials for Optoelectronics: A New Route Towards Efficient Devices at Elettra

The future of electronics will depend on more than simply making components smaller. It will also rely on our ability to engineer materials in which light and electrical charges can be precisely controlled, minimizing energy losses and power consumption. Achieving this requires a junction: a region where two distinct electronic environments meet, enabling the separation of charges generated by light.

An international research team investigated molybdenum disulfide (MoS₂), a two-dimensional semiconductor consisting of atomically thin layers. The approach is particularly elegant: rather than combining different materials, which can introduce defects at their interface, the researchers created two distinct electronic regions within a single MoS₂ sheet. The crystal lattice remains continuous, while the electronic landscape through which electrons move is modified.

Part of the material is placed in contact with an insulating substrate, chromium oxychloride. This interaction induces a small charge transfer, making the affected region less electron-rich than before. The result is a lateral n⁺–n⁻ homojunction: a single material with two distinct electronic environments, separated by a boundary that promotes directional charge separation.

At Elettra’s Spectromicroscopy beamline, micro-angle-resolved photoemission spectroscopy (micro-ARPES) provided direct experimental evidence of this change in electronic energy structure. The resulting device exhibited a photovoltaic response without an externally applied voltage, achieving an open-circuit voltage of 0.87 volts and demonstrating self-powered photodetection capabilities. This measurement represents more than a laboratory result: it marks the point at which a materials-design concept translates into experimentally observable device performance.