Phys. Rev. Lett. 112, 047403 (2014)

Gaël Reecht and colleagues have built the first single-molecule light-emitting diode, taking the latest step in device miniaturization and edging towards the realization of a molecular computer.

Reecht et al. suspended a single polythiophene molecule between the tip of a scanning tunnelling microscope and a gold substrate. They found that their device emitted light when current passed in a certain direction, with negligible effect when the polarity was reversed. The optical spectra measured by the team were insensitive to shifts in voltage, implying that the emissions corresponded to the intrinsic energy levels of the polymer itself.

Organic light-emitting diodes are already used in visual displays for mobile phones and digital cameras, offering high-quality luminescence at relatively low cost. The device reported in this study is reminiscent of these diodes, but boasts a significantly smaller scale than has previously been achieved.