Two-atomic-layered optoelectronic device enabled by charge separation on graphene/semiconductor interface

The Fermi level of graphene on different substrates usually changes significantly due to the interface difference between graphene and two-dimensional semiconductors. This feature opens many possibilities of manipulating optoelectronic devices by constructing graphene heterostructures through interface modification. Herein, we report the fabrication and optoelectronic response of an unconventional heterojunction device based on a graphene-MoSe₂ hybrid interface. Different from the traditional three or more layered structure where the semiconductor is sandwiched between two electrodes, this device contains only two atomic layers: the MoSe₂ layer serving as the photon absorber and the graphene layer functioning as the charge acceptor and both electrodes. This structure looks like short-circuited but shows an obvious photoelectric response, which is aided by electron transfers from MoSe₂ to graphene. The photocurrent generation is explored quantitatively with electronic dynamics of graphene aided with ultrafast measurements. The two-layered architecture simplifies the fabrication of atomic-thick optoelectronic devices, allowing the as-grown semiconductors to be directly used and eliminating the damage-prone transfer process.