Lighting up a single molecule has moved from a scientific curiosity to a controllable technology with profound implications. In a new perspective published in Science Bulletin, an international team of researchers from Nankai University, the University of Hong Kong, and Peking University details the rapid advances and future roadmap for “single-molecule electroluminescence” (SMEL)—the generation of light from electrical current flowing through a single, precisely positioned molecule.
The core of the technology is a molecular junction, where one molecule is bridged between two tiny electrodes. By applying a voltage, electrons are injected into the molecule, causing it to emit photons. The new article argues that four key “levers” now allow scientists to control this process with unprecedented precision: shaping the surrounding nanocavity to amplify light, engineering the molecule-electrode interface to prevent energy loss, applying electric fields to tune color and intensity, and designing custom molecular structures for desired properties.
Two main experimental techniques drive the field. Scanning tunneling microscopy (STM) methods provide atomic-scale resolution to map light emission, revealing fundamental quantum processes. Meanwhile, Single-molecule junction (SMJ) techniques, which chemically wire molecules between stable electrodes like graphene or carbon nanotubes, are better suited for building durable devices.
The potential applications are transformative. SMEL has already been used to create electrically driven single-photon sources—a crucial component for quantum cryptography and computing—with high purity. The authors highlight recent work where a 3×3 array of molecules all acted as identical single-photon emitters, demonstrating the scalability.
The most futuristic application is the single-molecule light-emitting diode (SM-LED), where each molecule acts as a programmable pixel. The researchers describe a prototype where a single molecule sandwiched between graphene electrodes could be switched “on” and “off” electrically, and even have its emission color changed by molecular design. The team further developed a single-molecule chip where light emission could be switched between fast (fluorescence) and slow (phosphorescence) channels, performing basic logic operations and real-time communication.
Despite progress, challenges remain, including low efficiency and the need for strict laboratory conditions. The authors propose that artificial intelligence will be key to overcoming these hurdles by rapidly designing optimal molecules and device structures.
The perspective concludes with a clear 3–5-year roadmap. By 2026, the goal is to achieve stable, room-temperature single-photon emission. By 2027–2028, the focus shifts to integrating multiple devices and creating red-green-blue (RGB) molecular pixels. The final phase (2029–2030) aims to demonstrate small-scale quantum information processing and integrate these molecular LEDs onto flexible surfaces.
This work is supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and Beijing National Laboratory for Molecular Science.
Science Bulletin
Literature review