Enhanced Near-Infrared Photodetection in a Mixed-Dimensional 0D/2D Heterostructure via Two-Photon Absorption

The perovskite nanocrystals (NCs) are featured with a strong two-photon absorption (TPA) due to the quantum-confinement effect, but suffer from a short transport distance of the photogenerated charge carriers isolated within the 0D spatial volumes. On the other hand, the 2D semiconductors of transition metal dichalcogenide (TMDC) possess a large carrier transport mobility across the homogeneous monolayer, whose atomic-scale thickness results in too poor an absorption capability to accommodate plentiful charge carriers upon light illumination. Here a solid film of the perovskite CsPbBr₃ NCs is deposited on top of a TMDC WSe₂ monolayer to form a mixed-dimensional 0D/2D heterostructure, whose charge-transfer interaction is facilitated by the type-II band alignment between the two composing materials. According to the ultrafast transient reflection measurements, the photogenerated holes in the CsPbBr₃ NCs can migrate into the WSe₂ monolayer within ≈800 fs to yield the current flow in a photodetector fabricated out of this 0D/2D heterostructure. When the CsPbBr₃ NCs are excited at the TPA wavelength of ≈1015 nm corresponding to the resonant bandgap transition, a responsivity of ≈7.5 × 10⁻⁵ A W⁻¹ is achieved that is the highest among all the currently-available values from the various photodetectors operated under the TPA conditions.