Perovskite quantum dots integrated with vertically aligned graphene toward ambipolar multifunctional photodetectors

Two-dimensional graphene (2D-Gr) has emerged as an attractive photoelectric material for light detection due to its wide spectral absorption. Nevertheless, the photo-responsivity is restricted by the weak light absorption and ultrafast recombination speed of photoexcited carriers. Herein, by replacing planar Gr with vertically aligned Gr arrays (VAGAs), followed by integration with FAPbI3 quantum dots (QDs), an ambipolar multifunctional photodetector is fabricated. A built-in vertical electric-field exists inside the FAPbI3 QD/VAGA hybrid architecture, of which VAGAs serve as the transport layer and FAPbI3 QDs serve as light absorbers. The Fermi level modification of VAGAs is realized by integration with FAPbI3 QDs, which will induce an increase in the built-in potential of the hybrid architecture and further facilitate the separation of photo-induced electron-hole pairs. The modification mechanism is experimentally explored and confirmed via scanning Kelvin probe microscopy (SKPM). Notably, the as-fabricated photodetectors exhibit an outstanding photocurrent response with excellent detectivity and responsivity at 1550 nm, which is mainly due to the synergistic effects of FAPbI3 QDs and VAGAs on light absorption, electron transportation, and vertical electric field. More importantly, systematic investigations into the transient optoelectronic properties of the as-fabricated photodetectors reveal that the response rate has a rise and fall time in the microsecond level, as well as outstanding long-term durability and reproducibility. Our present work adds to the portfolio of routes for creating high-performance graphene-based photoelectric detectors.