The frontier of nanotechnology and quantum optics has been dramatically advanced by recent breakthroughs in single-molecule electroluminescence (SMEL), a technique enabling the generation of light via an electrical current passing through an individual molecule. This revolutionary field has emerged from the interplay of precision molecular engineering and sophisticated nanoscale electronic design, facilitating unprecedented control of light-matter interactions at the sub-nanometer scale. In a newly published perspective in Science Bulletin, an international collaboration of leading scientists from Nankai University, the University of Hong Kong, and Peking University outlines the rapid developmental trajectory and ambitious roadmap of SMEL technologies poised to reshape the future of quantum light sources and integrated optoelectronic devices.
At the heart of SMEL technology lies the concept of the molecular junction, where a solitary molecule is chemically anchored between two nanoscale electrodes. This setup allows electrons injected through the electrodes to excite the molecule, which subsequently emits photons as the excited states relax. The finesse of this process depends on precisely engineered parameters that govern the electronic and photonic pathways. Critical to advancing this frontier are the four levers identified by researchers that facilitate exquisite control over the electroluminescence: the architecture of the nanocavity housing the molecule, interface engineering at the molecule-electrode boundary, electrical field modulation, and molecular design customization. Together, these factors dramatically enhance emission efficiency, spectral tunability, and operational stability.
Experimental exploration of SMEL is principally driven by two advanced methodologies. Scanning tunneling microscopy (STM) allows for atomic-scale visualization and manipulation, enabling direct correlation between the molecular configuration, electronic states, and photon emission patterns. STM’s spatial precision exposes the fundamental quantum dynamics underpinning SMEL, revealing the intricate electron-photon interplay within individual molecules. Alternatively, single-molecule junction (SMJ) techniques utilize robust chemical wiring of molecules between electrodes composed of conductive nanomaterials like graphene sheets or carbon nanotubes. This approach prioritizes long-term stability and device integration, essential for transitioning SMEL from laboratory curiosity to practical application.
One of the most striking demonstrations of SMEL’s transformative promise is the realization of electrically driven single-photon sources. Essential for quantum communication technologies, single-photon emitters must operate with high purity, stability, and controllability. The international research team reports the successful creation of a 3×3 molecular array in which each molecule acted as an identical single-photon source. This pioneering achievement not only proves scalability but also sets the stage for more complex quantum photonic circuits, where precise spatiotemporal photon control is paramount.
Beyond stationary single-photon sources, the field progresses toward the conceptualization and fabrication of single-molecule light-emitting diodes (SM-LEDs). These devices redefine the notion of display and lighting pixels by reducing each pixel to a single switchable molecule. The researchers describe a functional prototype based on a molecule embedded between graphene electrodes, capable of electrically toggling emission states on and off. Furthermore, molecular engineering permits dynamic modulation of emission color, enabling pixel-level customization unprecedented in classical devices. This tunability stems from deliberate chemical modifications that alter the molecule’s electronic structure and corresponding photonic output.
Innovations extend further into multi-channel molecular chips where emitted light can be switched between distinct photophysical pathways, such as fast fluorescence and slower phosphorescence. Such dynamic control enables the execution of rudimentary logic operations and real-time optical communication at the molecular scale. These SMEL chips harness the intrinsic quantum mechanical properties of molecules to perform computation and signaling tasks, charting a new course toward nanoscale photonic processors that could underpin future quantum computing architectures.
Nevertheless, despite substantial advances, the field faces significant challenges. The efficiency of photon generation remains limited, and the requirement for stringent laboratory conditions—often including low temperatures and ultra-high vacuum environments—hinders practical deployment. To overcome these obstacles, the researchers propose a critical role for artificial intelligence (AI). AI-driven molecular design and device optimization can accelerate the discovery of new molecules and architectures that combine photostability, high electroluminescence efficiency, and ambient condition operability. By integrating machine learning with physical modeling, the field anticipates exponential growth in performance and application scope.
The scientists present a detailed 3–5-year roadmap aimed at propelling SMEL systems into practical realms. By 2026, efforts focus on achieving stable room-temperature single-photon emitters with enhanced reliability, a milestone crucial for quantum communication technologies. The subsequent period (2027–2028) targets integration strategies that allow coupling of multiple devices and the creation of red-green-blue (RGB) molecular pixels, laying the groundwork for full-color molecular displays and complex photonic circuits. The final stage (2029–2030) envisions demonstrating small-scale quantum information processing and integrating molecular LEDs onto flexible substrates, potentially enabling wearable quantum technologies and flexible display innovations.
Supporting this cutting-edge research are substantial funding initiatives, including the National Key R&D Program of China, the National Natural Science Foundation of China, and the Beijing National Laboratory for Molecular Science. These resources empower the multidisciplinary teams to push the boundaries of molecular photonics, merging chemistry, physics, and materials science into a coherent platform for next-generation technologies.
Single-molecule electroluminescence epitomizes a convergence of quantum mechanics and nanotechnology that alters our fundamental ability to harness and manipulate light. As devices shrink to the scale of individual molecules, SMEL promises not only technological innovation but also novel physical insights into electroluminescent processes. This profound control over molecular-scale photons heralds a paradigm shift in how light sources, sensors, and optoelectronic circuits will be designed and implemented in the coming decades.
The collaborative work outlined in this perspective showcases the tremendous potential for SMEL to revolutionize the optoelectronics landscape. By mastering light emission at the atomic scale, researchers unlock a new regime of electronics where quantum coherence, molecular specificity, and photonic functionalities converge, creating pathways toward ultra-compact, energy-efficient quantum devices. As this remarkable field races from fundamental science to application, it beckons a future where single molecules illuminate a quantum technological era.
Subject of Research: Single-Molecule Electroluminescence and Quantum Light Sources
Article Title: Controlling Light at the Molecular Scale: Advances and Future Prospects of Single-Molecule Electroluminescence
News Publication Date: Not specified (anticipated 2025 based on DOI)
Web References: http://dx.doi.org/10.1016/j.scib.2025.12.020
Image Credits: ©Science China Press
Keywords
Single-molecule electroluminescence, molecular junctions, scanning tunneling microscopy, quantum light sources, single-photon emitters, electroluminescent molecular devices, molecular LEDs, nanocavities, molecular photonics, quantum communication, nano-optoelectronics, AI-driven molecular design
