Molecular Van Der Waals Heterojunction Photodiodes Enabling Dipole‐Induced Polarity Switching

Abstract Solid‐state devices capable of controlling light‐responsive charge transport at the molecular scale are essential for developing molecular optoelectronic technology. Here, a solid‐state molecular photodiode device constructed by forming van der Waals (vdW) heterojunctions between standard molecular self‐assembled monolayers and two‐dimensional semiconductors such as WSe 2 is reported. In particular, two non‐functionalized molecular species used herein (i.e., tridecafluoro‐1‐octanethiol and 1‐octanethiol) enable bidirectional modulation of the interface band alignment with WSe 2 , depending on their dipole orientations. This dipole‐induced band modulation at the vdW heterointerface leads to the opposite change of both photoswitching polarity and rectifying characteristics. Furthermore, compared with other molecular or 2D photodiodes at a similar scale, these heterojunction devices exhibit significantly enhanced photo‐responsive performances in terms of photocurrent magnitude, open‐circuit potential, and switching speed. This study proposes a novel concept of the solid‐state molecular optoelectronic device with controlled functions and enhanced performances.