N‐Type Superconductivity in an Organic Mott Insulator Induced by Light‐Driven Electron‐Doping

The presence of interface dipoles in self‐assembled monolayers (SAMs) gives rise to electric‐field effects at the device interfaces. SAMs of spiropyran derivatives can be used as photoactive interface dipole layer in field‐effect transistors because the photochromism of spiropyrans involves a large dipole moment switching. Recently, light‐induced p‐type superconductivity in an organic Mott insulator, κ‐(BEDT‐TTF)₂Cu[N(CN)₂]Br (κ‐Br: BEDT‐TTF = bis(ethylenedithio)tetrathiafulvalene) has been realized, thanks to the hole carriers induced by significant interface dipole variation in the spiropyran‐SAM. This report explores the converse situation by designing a new type of spiropyran monolayer in which light‐induced electron‐doping into κ‐Br and accompanying n‐type superconducting transition have been observed. These results open new possibilities for novel electronics utilizing a photoactive SAMs, which can design not only the magnitude but also the direction of photoinduced electric‐fields at the device interfaces.