Atomically thin 2D materials are promising candidates for extending Moore’s Law due to their exceptional geometric and electronic properties. However, the realization of ultrathin p–n junctions, as crucial components of modern electronic and optoelectronic devices, remains a significant challenge due to the limitations of traditional doping techniques used in bulk materials.
Researchers at Nanjing University of Posts and Telecommunications, Chizhou University, Henan University of Science and Technology and Yangzhou University have found that interlayer twisting can facilitate the formation of self-doped p–n junctions in 2D materials based on first-principles calculations combined with nonadiabatic molecular dynamics and nonequilibrium Green’s function methods.
By sandwiching a polarized In2Se3 layer between graphene layers, the team achieved twist-angle-dependent, abrupt p–n junctions with highly homogeneous self-doping properties. The interlayer twist effectively tunes the competitive relationship between the interface work function difference and the polarization potential, thereby controlling the direction of interfacial charge transfer.
Under photoexcitation, photogenerated electrons (holes) in the In2Se3 sublayer were rapidly transferred to the n-doped (p-doped) graphene in ∼50–230 ps, facilitated by strong electron–phonon coupling and small energy level difference, which is much faster than the recombination time in the In2Se3 sublayer (∼2–4 ns). A large spontaneous photocurrent was realized without an external bias voltage in the 2D stacked devices.
This work represents a promising twist strategy for advancing ultrathin electronic and optoelectronic nanodevices.
