Controllable Single-Molecule Light Emission by Selective Charge Injection in Scanning Tunneling Microscopy

Tunneling electron-induced light emission in scanning tunneling microscopy (STM) has recently been explored as a novel light source with tunable properties. Here, using first-principles-based atomistic simulations, we study the STM-induced luminescence of a single free-base phthalocyanine (H2Pc) molecule and propose a way to control the emission frequency of the STM molecular junction by precisely controlling the charge injection at different molecular positions. The luminescence is found to be directly related to the spatial distribution of the molecular states and thus depends sensitively on the tip position. Via careful refinement of the chemical structures, devices with desirable frequencies at different parts of the emitting unit can be designed. Our proposal has profound implications for applications in nanoscale optoelectronics and future hybrid electronic-photonic circuits.